Notes for Methods and Techniques of Social Research, Spring 2005

Grading formulas:

Total Score = ([Attendance]*0.1+[Quizzes and Assignments]*0.2+[Grade on Midterm One]*0.20+[Grade on Midterm Two]*0.20+[Midterm2 Makeup]*0.2+[Final Exam]*0.3)+[Extra Credit Points]   

Final Exam = ([Final Multiple Choice Items]*0.75+[Final Statistics Items]*0.25)

Quizzes and Assignments = ([Microcase Intro]+[Workbook 1]+[Workbook 2a]+[Workbook 2b]+[PercentQuiz]+[Workbook 3]+[Enrolling]+[Sampling]+[Workbook 5]+[Historical Trends]+[Workbook 8]+(2*[Human Subjects Letter])+[Crime Drop]+(2*[Excel Regression])+[Research Design])/17

April 26 - Review

Here are some points covered with multiple choice questions.   This material is covered in our text.  The "review glossary" at the end of each chapter is useful for review.:

Statistics questions will include:

percentages - row, column and total.  Covered in these notes. 
expected frequencies.  Covered in these notes
computation of mean
computation of standard deviation
computation of margins of error, covered in these notes 
use of an unstandardized regression equation to make a prediction. - this was part of the Excel Regression assignment and is also discussed in these notes.   A sample item is question 9 in the test called "Review Items for Final Two"
Use of standardized regression coefficients (beta weights) to interpret a path diagram.  This is explained in these notes

some WEB pages, one on Descriptive Statistics and one on  Inferential Statistics Review.  The class notes for October 1 (below) show how to calculate many of the statistics.  On December 10 we did some statistics review questions taken from last semester's final.


Depression Scale.   Weight and Mortality

April 21:

Content Analysis - "unobtrusive data"  Data created by a bureaucratic system, e. g. police records, or often by the media.  Television or Newspapers either because that is our interest, the media, or as a way of getting information, e.g., on crime reported in the news.

Similar to survey research, except that you do coding instead of interviewing.  Coding means that you assign numbers to phenomena that you observe.  Counting things.  Each of your variables is coded from the published information.

Conceptualization.
Measurement.  Reliability and Validity.

Manifest Content - what's it's about on the surface
Latent Content - things that we infer about the content, e.g., does the writer sound angry?  Indignation, sexy?
A Content Analysis Study of Editorial Cartoons.
 A Content Analysis of Internet-Accessible Written Pornographic Depications.




April 19

Experimental Research.   Experimental Designs.  See the graphs in the book or on Trochim's WEB site:  Types of Designs

Essential characteristics:

  1. Two or more groups are matched, usually by random assignment, sometimes by a kind of stratified random selection, e.g., an equal number of men and women or black sand whites in each group.  But the key is random assignment so that the groups can be assumed to be the same on all variables.  "Quasi-experiments" are when we use groups that are pretty much the same but we didn't assign people at random
  2. The Independent Variable is "manipulated," i.e., it is applied to one group and not to the other
  3. Change in the Dependent Variable is measured
Experiments can be done:
  1. In laboratory settings with volunteers, e.g., student volunteers
  2. In institutional settings such as prisons, hospitals, rehabilitation centers, etc., where people are assigned to treatment groups
    1. New drugs and medical treatments generally must be shown to work in experiments before they are approved for use.  Often,Stanley Milgram's Obedience Experiment from http://www.new-life.net/milgram.htm treatment is compared to a placebo.  These experiments are usually "double-blind," to control for the psychological effects of knowing one is getting treatment.  This is a way of controlling subject bias and experimenter bias/
    2. In criminal justice, one might do an experiment comparing a "half way house" to drug treatment program to a prison term for offenders.  To do this, you would have to get the judge to assign offenders to different programs at random.  Ethical issues are raised here and there are likely to be objections
  3. Occasionally in natural settings, for example
    1. welfare reform experiment, assign some recipients to the old program, some to the new.  This didn't work very well, there were errors in the group assignments and the women often forgot which group they were in anyway
    2. vaccination experiments
    3. guaranteed annual income experiments
Although logically experiments are the most rigorous way to test causal hypotheses, there are practical problems: April 14:  Field Research:
Some examples of field resarch:
Margaret Mead, the only anthropologist (or sociologist) to get her own postage stamp, won fame through field work, primarily her book Coming of Age in Samoa.  Later, this book was denounced by anthropologist Derek Freeman in his book Margaret Mead and the Heretic : The Making and Unmaking of an Anthropological Myth.Anthropologists have come to Mead's defense, and have restudied the case, but I would have to agree with your text that "had Mead come back from Samoa with an accurate ethnographic report, it would not have made her famous."  Here is the NY Times Review of Freeman's critique of Mead.
     More recently, there has been a raging controversy about the book Darkness in El Dorado about research on the Yanomamo in Venezuela is the latest ethical controversy, which also raises important methodological questions.  Many of the book's allegations, however, have been contested by the National Academy of Sciences.
  The combining of fiction with factual research is increasingly common both in anthropology and in biographies.  Sometimes this is openly done as a literary form, in other cases such as that of Rigoberta Menchu, it is only admitted when critics discover it.   The Rigoberta Menchu Controversy by Arturo Arias. 
There are many problems with field research:  ethical issues, problems of reliability and validity when data are gathered by only one researcher, etc. A controversial book is Laud Humphrey's Tea Room Trade, which raises ethical issues. He studied gay sex in a men's room in a park in St. Louis, without informing the participants what he was doing.
    Field researchers sometimes seem to find examples that fit their preconceptions, and their work is often ignored by those who do not like the results, e.g., Leon Dash's book When Children Want Children and Rosa Lee which are just ignored by welfare advocates who prefer more sympathetic treatments.  One of the best field studies is Kathryn Edin's book Making Ends Meet. which is highly sympathetic to the mothers.  However, Edin collected statistical data as well her illustrative observations.  The statistics showed that almost none of the mothers actually lived off their grants alone.  Eli Anderson's book Streetwise on men in a Philadelphia ghetto has been well received, in large part because goes beyond one-sided advocacy.
    A great strength of field work is observing behaviors that the people themselves don't understand or aren't even aware of., or at any event, are unable or unwilling to talk about.  Anthropologist Jules Henry spent a week living in each of the homes of several children who had grown up mentally ill, trying to discern patterns in the family interactions that contributed to the illness.   Myra Bluebond-Langner's book The Private Worlds of Dying Children has been very influential;  she has just published a sequel called In the Shadow of Illness : Parents and Siblings of the Chronically Ill Child    Field reserch offers a richness of description and possibility of new insights that is unparalled by any other method.  Unless it is supplemented with other methods, it does not provide statistical data, and it is hard to replicate.
    Myra Bluebond-Langner of our Anthropology Department wrote a classic, The Private Worlds of Dying Children, and more recently, In The Shadow of Illness.

Coming of Age in New Jersey

The Corner.

Black American Students in an Affluent Suburb.  by John Ogbu

Commentary on Ogbu's research

Many scholars who have disputed those findings rely on a continuing survey of about 17,000 nationally representative students, which is conducted by the National Center for Education Statistics, an arm of the federal government. This self-reported survey shows that black students actually have more favorable attitudes than whites toward education, hard work and effort.

But that has by no means settled the debate. In the February issue of the American Sociological Review, for example, scholars who tackled the subject came to opposite conclusions. One article (by three scholars) said that the government data were not reliable because there was often a gap between what students say and what they do; another article by two others said they found that high-achieving black students were especially popular among their peers.

"It's difficult to determine what's going on," said Vincent J. Roscigno, a professor of sociology at Ohio State University who has studied racial differences in achievement. "'I'm sort of split on Ogbu. It's hard to compare a case analysis to a nationally representative statistical analysis. I do have a hunch that rural white poor kids are doing the same thing as poor black kids. I'm tentative about saying it's race-based."

Indeed, Professor Mickelson of the University of North Carolina found that working class whites as well as middle-class blacks were more apt to believe that doing well in school compromised their identity.

All these years later, Professor Fordham said, she fears that the acting-white idea has been distorted into blaming the victim. She said she wanted to advance the debate by looking at how race itself was a social fiction, rooted not just in skin color but also in behaviors and social status.

"Black kids don't get validation and are seen as trespassing when they exceed academic expectations," Professor Fordham said, echoing her initial research. "The kids turn on it, they sacrifice their spots in gifted and talented classes to belong to a group where they feel good."



April 12:  We went over The Crime Drop in America: Disaggregating Violence Trends.
April 7:  we learned how to plot regression lines on graphs in Excel
April Fifth.  Department Newsletter

March 31,  Second Midterm:  Grading formulas:

Quizzes and Assignments = ([Microcase Intro]+[Workbook 1]+[Workbook 2a]+[Workbook 2b]+[PercentQuiz]+[Workbook 3]+[Enrolling]+[Sampling]+[Workbook 5]+[Historical Trends]+[Workbook 8])/11

Grade on Midterm Two = 0.8*[Midterm Two Multiple Choice]+0.2*[Midterm Two Statistics]

Estimated Course Grade = ([Attendance]*0.1+[Quizzes and Assignments]*0.2+[Grade on Midterm One]*0.35+[Grade on Midterm Two]*0.35)+2

March 29  Amputation Survey. mentioned in class.  General review going over these notes.  In your review, you may find it better to start with the older notes at the bottom of the file.  The exam will cover chapters one, two, three, four, five, seven and eight plus material covered in class (see the class notes) including path analysis and the computation of margins of error.  It will NOT include the use of regression equations to calculate predicted scores on dependent variables (we'll do that after the midterm).

March 24

Capital Punishment and Homicide Rates: Sociological Realities and Econometric Distortions, a paper which is in WEBCT.

The ABSTRACT summarizes the main point of the paper:
Sociological methods have consistently succeeded while econometric methods have failed in research on capital punishment and homicide.  But econometricians aggressively promote their findings in public policy venues, while sociologists are less assertive.  This is due to cultural differences between the disciplines, and to a philosophy of science that values falsification of hypotheses over progress in answering research questions.  This problem has occurred and is likely to reoccur in other policy areas where sociologists are insufficiently asserting in defending their accomplishments.

  1. In this paper the "sociological method" discussed is comparative analysis as discussed in Chapter 8 of our text, especially the use of time series graphs and scattergrams.  Several are at the end of the paper.
  2. The "econometric" method is multiple regression, discussed in chapter 5 of our text.
  3. The dependent variable is the homicide rate in a state, the independent variable is either the presence or absence of capital punishment in a state or the number of executions in a given year in a state.
  4. Econometric students have given highly variable results, many econometricians conclude that each execution deters a number of homicides, thus saving lives.
  5. But others conclude the opposite, showing the importance of reviewing the literature comprehensively instead of just relying on the studies that happen to confirm one's position.
  6. Why have the regression studies failed to give a consistent result:  1)  the available data are limited and do not meet the assumptions required for regression analysis, especially a normal distribution  2)  the State of Texas is a prominent outlier, dominating the results  3)  there are so many different ways to adjust the data to fit them into a regression equation that researchers seem to be able to come up with any result they believe in.
  7. This has been the case in many other areas, including gun control, race and intelligence, assessing the effects of minimum wage laws, etc.  You can find an economist on either side of the issue, just as you can find a psychiatrist on both sides in many criminal trials.  This is why Harry Truman said he wanted a "one-handed" economist.
  8. A better method is to examine the data in graphs, then interpret it using you qualitative knowledge of the states in question.  This method does not distort the data by assuming it fits into normal, linear distributions.
  9. People who used this method have agreed that no effect of capital punishment on homicide rates can be found in the available data.

We will go over Exercise 8 in the Workbook. 

Discussion of paper on Capital Punishment and Homicide Rates, which is available in WEBCT.  An older, more popular version is at online

March 21

Mr. Goertzel:
Guess what!  As the weeks have been passing, and you've been teaching 
us all this research data stuff... I've asked myself a hundred times -
"when the hell am I ever going to need to know all of this?"

The past few days I was in Chicago with J'ona Meyer for a CJ
convention and during one of the presentations a gentleman put up his data on a
projector......and I was ASTONISHED that I understood EVERYTHING he was
talking about - from his variables, to the standard deviation, to it's statistical
signifigance, etc.! I'm happy to report I'm actually learning
something of use in your class! Had I not taken this class, I would have sat there
feeling like a total dummy not knowing a thing what he was talking about.

Thanks - Denise Gilboy

Comparative Research Using Aggregate Units, Chapter 8 in the text.  This research method uses data about social or geographic units.  Consistent criminal justice statistics are important for evaluating CJ policies.  Thorsten Sellin, a professor at Penn, was instrumental in getting consistent CJ statistics established.  We can find examples on the Bureau of Justice Statistics WEB site.

Comparative methods are particularly useful for studying change because we can get data about trends over time.  Look, for example, at some Trend Graphs taken from the "Historical Trends" module in the Professional Microcase.  This is available in the computer center on the networked Windows computers (click on Statistics and Microcase on the Windows menu, then open "Microcase Curriculum Plan 2003-2004 and load the TrendSmp data set.  Our next assignment requires using this data set in the computer lab..

Some concepts:

Rate:  A statistic that reduces numbers to a common base.  The base is often, but not necessarily, the total population in an area.  If we are looking at voting participation, we might compute rates using the base of the number of adults 18 or over.  If we are trying to predict an election, we might use a base of registered voters. 

A crude birth rate is the number of births per 1,000 population.  Fertility rate is the number of births per female during her lifetime. 

Time Series analysis:  uses time periods as the unit of analysis, looks at how things change over time often in one case.   A lagged time series takes into account the time it takes for one variable to influence another, thus incarcerations in one year might be related to crimes in the next year.

 Cross-sectional analysis compares a number of cases at one point in time.

Reliability:  are statistics computed the same way in different geographic units or different time periods.  This causes all sorts of problems - it is better to imporve statistics, but doing so causes us to lose comparability. 

Validity:  do the statistics measure what we want them to measure.  Crimes reported to the policy are not a valid measure of the amount of actual crime, especially for crimes that are often not reported. 

Case oriented vs. variable oriented.  The case oriented approach is more qualitative, although quantitative trend data can be used.  The variable oriented approach assumes that the same variables are causally related in the same way in a large number of cases, e.g., "capital punishment" and "homicide rates" in a number of states or countries. 

Outliers:  especially in variable-oriented research, it is important to look for exceptional cases that are very different from the norm.  These tend to cause a disproportionate impact on our results. 

Lagged:  Using statistics from past years to predict events in current years.  This is done because our theory says that causal linkages take some time to take place.



March 10

To understand regression, we first need to understand what it means to plot an equation on a graph.  If we draw two coordinates on a piece of paper or on the whiteboard, we can draw a Cartesian coordinate plane.  with an x-axis (for our independent variable) and a y-axis (for our dependent variable).  We can then plot lines on this graph by using a regression equation:

    Y    =    a   +   b   X.       where X and Y are our variables, and a and b are parameters or fixed numbers given to us by the computer software.

     For example, plot the following lines:
     If a is zero and b is one, then Y = X.  We can say:  if X is 0, Y is 0.  If X is 2, Y is 2, etc.  If we plot these points on the graph we get a straight diagonal line going from the lower left to the upper right (to be demonstrated in class):
      If a is one and b is one, we get a line parallel to the first, but one notch up.
      If a is 0 and b is minut one, the line will go down...   etc.
                                                  
  is a method that computes equations like this to fit straight lines to bivariate relationships between continuous or linear variables.  It works best when the variables are "normally distributed," i.e. when they fit a bell-shaped normal curve with most of the cases near the mean and few extremes. We can see how regression works best by using the scatterplot program in Microcase and the USA data set which has many continuous variables using the US States as the unit of measurement. and clicking on "reg line".  For example, the graph of  % college and Median family income (open Microcase to see this).

At the bottom it says "Line Equation   Y = 15254 + 902.229 X.   This is the equation straight line that appears on the graph. 

What does it mean to say that it is the equation for a line?  It means that if you use the equation to plot points on a graph they will look like that line.  The more general form of this equation is Y = a  + b X  where:
      X is the independent variable  (in this case % college)
       Y is the dependent variable (in this case Med Fam $)
       a is the "intercept" - this is a "parameter" of the equation which means it stays fixed while the variables vary
        b  is the "unstandardized regression coefficient" - it is also a paramater. 
      The software computes the equation for us, which is called "fitting a regression equation to the data".

We can also do Multiple Regression which means we have more than one independent variable.  For example, we could use both the %College and the %urban and the %smokers to predict median family income.  We would have an equation such as:

            Y =  a   +  b1X1 + b2X2 + b3X3         with as many b's and x's as we include variables

With multiple regression, however, we can't plot a scatterplot unless it is three-dimensional.  Going beyond three dimensions is impossible to visualize.  Plus, it is hard to compare the b's because they are measured in different units.  So we create:

standardized regression coefficients  also referred to as BETA Coefficients  which vary from -1 to 0 to +1 like correlation coefficients.  These are used to compare how well each of the independent variables helps us to predict the dependent variables.  We can also construct complex networks of regression equations where    A, B and C  predict D,  then D and E predict F, etc. etc. This method is best illustrated with path analysis, a way of  graphing complex regression models. 

Path analysis is useful because it enables us to visualize our ideas much better than we can when we see a list of equations.  It approaches the complexity of our qualitative thinking.  Unfortunately, however, the mathematics requires a lot of simplifying assumptions.   The method does not really PROVE that the model is correct, it simply illustrates our ideas and shows the strength of the correlations.  It assumes linear relationships, which we often do not have.  In my opinion, graphing trends and interpreting them in view of our qualitative knowledge is more valid, although less "hi-tech".  I have published two articles arguing this point in the Skeptical Inquirer magazine.  Here is a link to the text of one of them in case you are interested:  this is something we will come back to later in the course.

Before getting into the criticism, however, we can learn how to do a path analysis.  Although the mathematics is a bit complex, the computer does it for us, so it is not actually difficult.  You can find the basics ideas in  Brief Intro to Path Analysis. If anyone wants a longer introduction with more examples it is available.

For the exam, you should know how to set up the regression equations to fit a path diagram. All you have to do to actually do a path analysis is put these equations into Microcase. The rules are the follows:

  1. There should be a regression equation for each variable that has an arrow pointing towards it.
  2. For each equation, the variable having arrows pointing into it is the dependent variable, and goes to the left of the euqals sign.
  3. For each equation, the variables on the left of the dependent variable that have arrows pointing into it are the independent variables.  These are listed to the right of the equal sign and connected with + signs.
  4. There is no need to include an intercept, because we are interested only in the standardized regression equations or beta weights.
An example.  Suppose we have the following diagram:

Perot Vote Input Path Diagram

For this diagram, we would need the following equations:

vote for perot =  alienation from government + alienation from society + finances worse

    alienation from government = status deficiency

     alienation from society =  status deficiency

If we got measures for these variables from a National Election Survey (Status Deficiency would be an index we would have to calculate), we could use the Regression procedure in Microcase to enter the three regression equations and get Beta coefficients which we could put on the diagram, as follows:

Output Path Diagram

October

March 8:

Today we will look at testing causal hypotheses.  On page 93 in the text, we have the example of the relationship between Height and Liking Basketball.  This is anIV and a DV.  An obvious TEST VARIABLE is Gender.  This would be Antecedent, Gender determines both your height and liking for basketball.  We could draw this as a path diagram (on board).

When we introduce the control, we split the table into two parts, e.g.,

                             Males                  Females                 Total
                        Tall     Short           Tall   Short         Tall    Short

Likes BB           85%    85%            25%   25%         65%    45%
Does Not           15%    15%            75%   75%         35%    55%

Total                 100%  100%          100%  100%      100%   100%

In the real world, things are never this sharp.

Let's look at some real data, using FEAR WALK, PLACE SIZE and R.INCOME from the GSS data set:

In the total sample, the low income respondents are more likely to feel there are areas near them where they should fear walking.  However, this effect disappears for some of the respondents when we control for the size of the town in which they live.

To make it a finished Table:
                Small Town or rural         Small City        City/Surb          Total
                  Low  Med  Hi             Low Med Hi        Low Med Hi      Low Med Hi

Fear Walk         30%  27%  24%            48  42%  20%      56  41  43     51%  39%  41%
No Fear           70%  73%  76%            52% 58%  80%      44% 59% 57%    49%  61%  59%
                     p = .710                p = .043           p = .000       p=.000
                     N = 251                 N = 133            N = 1253      N = 1637
 

To to a more complete causal model of Fear of Walking at Night, we should introduce more variables.  Some of them may be in our data set, others now.  

What variables should we look at?

Variables      Hypotheses
Gender           Females more fearful than males.
Age              Elderly more fearful, also Children.  Might be curvilinear.
Crime Rate       People in high crime communities
Street Lighting
Freq of Patrols
Graffiti, Broken Windows, Trash, other indicators of an "out of control" neighborhood
Bicycles
Number of Pedestrians
Physical Shape
Training in Self Defense

We can examine some of these variables with our data.  We may find it useful to use regression rather than cross-tabulation.
We can also use pages 114-122 in the workbook as examples..

March 3:
 
Causal Analysis - Chapter 5.

The Art and Science of Cause and Effect. (powerpoint)

Probabilistic cause, not an absolute cause, not a cause that is sufficient or necessary.   "Cigarette smoking causes
cancer."  WHat we mean is, smoking cigarettes increases the likelihood of getting cancer.  How much?

There are multiple causes for everything.  What we want to find out is how much each thing contributes.  There are also
causal linkages, or indirect causes.  A causes B and then B causes C.

Diagraming causal models.  We put the dependent variable at the right.  We draw arrows going into it for each causal
variable that effects it directly.  Then we can have arrows that go into the arrows, steps into the causal analysis, as in
this sample file:
http://crab.rutgers.edu/~goertzel/homomale.htm

Criteria of Causation - how do we know that something is a cause of something else.

1.  Time Order.  The cause comes before the effect.  Sometimes we sort out the time order theoretically, we assume that
education preceeds employment.  Or we can use a research design that involves gathering data at two points in time.  If
you don't have measurements at two points in time, this is shaky.

2.  Correlation.  The two variables vary together.  When one is high, the other is high OR when one is low the other is
high.  This gets at the degree of causation, the higher the correlation the strong the causal relationship.

3.  non-spuriousness,  we want to know that the correlation is not cause by something else.  We can test this with an
experimental design, if feasible.  Or we can use statistical controls, which are not quite as convincing but its all you do
in many cases.

We test for non-spuriousness by introducing controls.

Causal Models:  representations of the complex causal relationships between variables.  Variables have different causal roles, but this is determined by our causal our causal model, it is not inherent in the variables.   One person's cause can be another's effect.

Dependent Variable - that is what we want to explain.  Often these are opinions or behaviors

Independent Variable - what we use to explain it.  Often there are traits or physical characteristics, e.g., sex or race,
almost always independent.

If you study the relationship of race on voting, for example, race would be independent and voting dependent.

Antecedent variables, things come before the independent variable.  This helps us to deal with a causal chain.
Antecedent variable cause IV which causes the DV.
If the antecedent variable "explains" the relationship, we have an "explanation", we say it is "spurious".

Intervening Variables, this that are intervening, e.g.   Race determines ideology which determines the vote.
This is an "interpretation" it tells WHY the causal relationship exists.
Path Models:  a way of graphically expressing complex causal models.

Example:  Determinants of Adult Homosexuality in White Males.

Example:  The Seattle Social Development Project. 

  Today we will learn the formula for margins of error for mean scores:

If you need a margin of error for a mean score (an average such as income in dollars or scores on a test), you need to know the standard deviation (sd) and the sample size (N). Ignore any other information you are given, including the size of the population.
Use the following formula: M = 2 * sd / SQRT(N).

Here is an example question:  A study of Rutgers Camden Sociology Department graduates showed that the mean annual salary was $55,000 with a standard deviation of $3500. Three hundred graduates were sampled. What is the margin of error for this statistic?    Answer:  M =   2 * 3500/SQRT(300)  =  7000/17.3205  = $404.15.  Note that this is a dollar amount, since the question was in dollars.  It is not a percentage.

What is the confidence interval for this mean score?  The answer is $55,000 plus or minus $404.15, or $54,595.85  to $55,404.15
The formula for percentages or proportions is:

m = 1/sqrt(n)   



March 1:
SAMPLING is used when we are interested in studying a population that is too large for us to study each individual.  The first step is to define the population we wish to make statements about, e.g. adults in New Jersey, probable voters, people convicted of felonies, graduates of our department.  We might want to study the entire population of the USA.  If we try to collect data from everyone, this is a census.  The Census Bureau does this once every decade, and misses a lot of people.  Everyone else does sampling, we select a cross-section to represent the population.  If you try to study the whole population, you often fail to do a good job.   Gallup:  How Polls are Conducted.

Size of the sample.  How big of a sample do I need? Size of the sample does not depend on the size of the population.

How do we select the sample size?  Decide on the margin of error you will tolerate?  Margin of error is equal to one divided by the square root of the sample size.  Sample of 400, the square root is 20.  1/20 = .05 or 5%.  If you interviewed 400, 300 were white, 50 were black and 50 were others.  For the blacks, with a sample of 50, we would have a 14% margin of error.  For the whites, with a sample of 300, we would have a 5.8% margin or error.

Take 300, the square root of 300 is = 17.32     1 /17.32 = .0577  * 100 = 5.8%

Sample statistic - what the sample says
population parameter - what the real figure is
Even if the sampling is done well, the response rate is less than 100%.
Weighting is done to make the sample more like the population.

This formula is for  proportions or percents (if you move the decimal over two)
  m = 1/sqrt(n)  
  Solve for N:      m2 =  1/n      n * m2 = 1     n = 1/ m2    If we need a margin of error of 3%, or .03.   n = 1/ .032

  If you have a sample size and need to know the margin of error, use    m = 1/sqrt(n)

   If you are given a margin of error and asked how large a sample you need, use  n = 1/ m2

          In these formulas n = the size of the sample (not the population).    m = the margin of error expressed as a proportion, not as a percent.  Thus, if the questions says "we need a margin of error of 5%, then m = .05.   

If our sample is stratified, this means we really have several sub-samples and we need the same size sample for each of them, regardless of the size.  For example, if we want sample white, black and Hispanic respondents and make statements about each group, we need the same size sample of both regardless of their size in the population.  Thus, if we need a margin of error of 5% for each of the three groups, then the answer is  3 * ( n = 1/ m2 ).

If you need a margin of error for a mean score (an average such as income in dollars or scores on a test), you need to know the standard deviation (sd) and the sample size (N). Ignore any other information you are given, including the size of the population.
Use the following formula: M = 2 * sd / SQRT(N)

Terms:

Margin of Error:  How much a sample statistic is likely to vary from the population parameter.  We say that we are 95% sure that the sample is not off by more than the margin of error.  How this is presented in NY Times.  "19 out of 20" is another way of saying 95%. 

 Confidence level:  we always use a 95% confidence level.

Confidence interval:  the range within which we think a statistic would fall, e.g., if the margin of error is 3% and the sample statistic is 67%, the confidence interval is from 64% to 70%.  We are 95% sure that the true figure is within this limit.

All of this assumes a simple random sample, which means that each person (or other sampling unit) in the population has the same chance of appearing in the sample.  In practice, however, we often do not use simple random samples, for several reasons:
  1. we may not have a list of the population.  If we do not, we first divide the sample into sub-groups of some kind (census tracts, blocks, classrooms, organizations, depending on the nature of the study).  We then sample the subgroups and list the populations in them .  This is called cluster sampling
  2. We may be interested in differences between sub-groups of the sample and need to make sure we have enough of them.  In this case we select random samples of each of the relevant sub-groups, and weight the results appropriately.   This is called stratified sampling. 
  3. Sometimes we just go down a list, which is called systematic sampling.  This gives the same results as simple random sampling, unless there is some systematic ordering to the list that causes a distortion
  4. Sometimes we use non-random or "quota" sampling.  This is done for convenience, or because we just want to know what the range of differences is without putting numbers on them.
Feb 24:  midterm exam.  Grades are in WEBCT. 

Grading formulas:

Quizzes and Assignments =
([Microcase Intro]+[Workbook 1]+[Workbook 2a]+[Workbook 2b]+[PercentQuiz]+[Workbook 3]+[Enrolling])/7

Grade on the Midterm=[Midterm One Stats]*0.25+[Midterm One Multiple Choice]*0.75

Estimated Course Grade =  ([Attendance]*0.1+[Quizzes and Assignments]*0.2+[Midterm One Total]*0.7)


Feb 22 was the review for the midterm.

Feb 17:   Why do we gather statistics?  One reason is to make policy decisions.  We decide whether policies we are following are effective by gathering statistical data.  An example is a book on "The Crime Drop in America" which is based on crime statistics. It is very difficult to establish WHY the trends are as they are Often it is discouraging, e.g., giving out speeding tickets does not cut traffic accidents. 

Another purpose is for evaluating local efforts, a policy that is often referred to as "compstat" which just an abbreviation for "computers and statistics"  What this means is that policy units are evaluated according to the statistics in their precinct or other jurisdiction.  New York City and Philadelphia have done a lot of this.  San Diego had an exemplary web site communicating this data to the public, but its mapping software doesn't seem to be up at the moment.  Camden let its mapping system go dead and has promised to get it started again.  Some good work is being done by community groups, who have produced some power points on Camden Crime and the Camden police that are on our WEBCT site. 

Links to sources of crime statistics are on a separate page

Feb 15:

We did an in-class exercise with the Keirsey Temperament Sorter.  Here are some hypotheses we can test:


Sociology
Criminal Justice
total
Thinking
40% expected percent
37.5% observed sociology majors who are thinking
3  observed frequencies
3.2 expected based on the 40/60 hypothesis
2.7 expected based on the null hypothesis of no difference
60% expected percent
33.3% cj majors who are thinking
6 observed freq.
10.8 expected based on the 60/40 hypothesis
6.2 expected based on the null hypothesis of no difference
9
Feeling
60% expected percent
62.5% sociology majors who are thinking
5 observed freq
4.8 expected based on the 40/60 hypothesis
5.2 expected based on the null hypothesis of no difference
40% expected percent
66.7% CJ m ajors who are feeling
12 observed freq
7.2 expected based on the 60/40 hypothesis
11.8 expected based on the null hypothesis of no difference
17
Total
100%
8 people
100%
18 people
26


Bush
Kerry

Thinking
1
3

Feeling
4
20






In this second case, it is obvious that there are not enough "Bush" voters to provide an adequate sample.  The bias in the "feeling" direction is strong.

These hypotheses relate to findings from the Alumni Survey done last semester.

Scaling or index construction is when we use a number of items, such as questionnaire items, to measure a more general concept.  We can do this by adding them up (in which case your text would call it an "index", although many people still use the term scale) , or they may be ordered from lowest to highest (in which case it is a true scale as the term is used in your book).  Your test is an example.  I just add up the points, to measure the general variable "knowledge of research methods as covered in the first part of the course."  Another approach would be to rank the items from easy to hard and see which you could do.  This is tricky, because some people can do the hard ones and not the easy ones.  When we make an index or scale, we get measures that can be treated as interval, even if they are not strictly interval.  Scaling methods can be more precise, but these are not used as often in sociology or CJ because they are more difficult and the added information is not always needed.

Scaling methods include Thurstone and Guttman Scaling Likert or summative scaling is actually a method of "index" construction as defined in our book.  A powerpoint on Thurstone scaling
  For example, we could scale the seriousness of crimes.  There are various methods of measuring this. - paired comparisons means asking a sample of people to rate crimes based on their perceived seriousness.

A very popular test is the Myers-Briggs Type Indicator, based on Jungian personality theory.  You can take a free version online.  Another is the Keary Temperament Sorter.   

Feb 10

Reliability -  you get the same thing over and over.  Consistency.
         inter-rater - two different raters get the same answer.
         test-retest, if you take it twice the answers are the same.
           internal consistency - are theitems on a test consistent.  Chronbach's alpha is a statistic that measure inter-item reliability.
    Validity  is it "really" measuring what it is supposed to measure.
          Face Validity - does it look right?
          Predictive or criterion validity - does it predict what we want to predict, some "true" measure.  SAT test predicts college or law or medical school grades.
          Convergent validity -  do several measures give the same result.
             
          Construct validity - does the measure perform as our theory says it should.  We use this when we have no criterion.
  
This is the most difficult, it is used when things are inherently difficult to measure. 

We will examine some materials in a chapter called "Connecting Conceptualization and Measurement" that will be distributed in class.

                  An example:  a study of UFO Abduction Status.



February 8

Measurement means putting observations into categories.  Often these categories are given numbers, although not always..   Sometimes we do this just to keep track of things, e.g., each American has a social security number, we have a library number, a student number, etc..  But often the numbers give us more information than that, e.g., the NJ driver's license gives height in feet and inches.  It also gives sex and eye color, which are described in words but could be given arbitrary numbers.  But the numbers given for height are not arbitrary. In some sciences, e.g., astronomy, numerical measurement has led to important insights, e.g, to understanding the motion of the planets.  This is because our observations can be summarized with mathematical equations that enable us to predict events.

 When we measure something, we need to be clear exactly what the measure means.  Especially when we use a number, we want to know what it means.  What is a number?  It is not so obvious as one might think.  Bertrand Russell said "A number is the class of all classes similar to a given class."  I.e., all sets of three have something in common, which we could call "threeness."
 
Levels of Measurement.  What is our measurement really saying about the relationship between the values?

Dichotomous Measurement -   Two and only two categories.  Can be a natural dichotomy or a  "dummy variables" - we take a complex variable and divide it into a series of dichotomous variables.  

Nominal Measurement.  Categories that could be put in any order.
      Catholic, Protestant, Jewish, Moslem, LDS, Buddhist, Episcopalian, Baptist
                       variable one, category of religion, variable two denomination.
            Mental illnesses (DSMIV) e.g.,  adjustment disorder, borderline personality disorder, paranoid schizophrenic
               Crimes:   burglary, assault, murder.  What do these terms mean?  Look at the US Criminal Code

  Each individual should go into one and only one category on a variable, one value on a variable.  
For example:  What is your favorite food, we have a long list, but each person is allowed only one.
       Sorting people into categories must be reliable and accurate or valid.

Ordinal Measurement.   Here we have categories in a logical order.       Very short, short, medium, very tall, tall .  Often we take continuous variables and make them ordinal.    Income:   Under $20,000   $20 to 40,000  $40 to 60,000   $60000 plus.

Interval Measurement:   TEMPERATURE IN FAHRENHEIT OR CENTIGRADE, 0 degrees is not the absence of heat.  How about the day that the "temperature doubled" in New York City?

Ratio Measurement:    Income in dollars:  a continous numerical value PLUS a meaningful zero point.  Height in inches. 
 
Scaling is when we use a number of measures, such as test scores or questionnaire items, to measure a more general concept.  This often allows us to move to a higher level of measurement.  For example, we can add up test score items them up (in which case your text would call it an "index", although many people still use the form scale) , or they may be ordered from lowest to highest (in which case it is a true scale as the term is used in your book).  Your test is an example.  I just add up the points, to measure the general variable "knowledge of research methods as covered in the first part of the course."  Another approach would be to rank the items from easy to hard and see which you could do.  This is tricky, because some people can do the hard ones and not the easy ones.  When we make an index or scale, we get measures that can be treated as interval, even if they are not strictly interval.  Scaling methods can be more precise, but these are not used much in sociology or CJ.  For example, we could scale the seriousness of crimes.  There are various methods of measuring this. - paired comparisons means asking a sample of people to rate crimes based on their perceived seriousness.

One of the reasons we have to be clear about levels of measurement is that the statisitcs we use depend on how the data are measured. 

Statistics for Nominal Data:    Percentages and Chi Square   The percentages are descriptive (they summarize our data), the chi square is inferential (it tells us if we can generalize from our sample).   Survey data usually produces nominal (or ordinal) statistics.   Cramer's V is a correlation coefficient for nominal data, scores on it vary from 0 to 1, but there are no negatives since the data are not ordered.

Statistics for Ordinal Data:  The median is the only statistic we have covered that is specifically designed for ordinal data - it finds the case in the middle once all the cases are sorted in order.  There are correlation coefficients for ordinal data which you can find on the "statistics" page for crosstabulations (gamma, tau) but it is more common to use interval statistics (Pearson's r) or nominal ones (Cramer's V) with ordinal data.

Statistics for Interval Data:   Scattergrams, means, standard deviations, correlation coefficients.  Tests of statistical significance for correlations.



February 3:

Today we will begin with Amar Patel's Chi-Square lesson.   This covers the concept of expected frequencies and observed frequencies, and introduces the concept of "fairness", the difference statistic and the chisquare statistic.  These are applied to problems where the expected frequencies are given by a null hypothesis of "fairness".

We can apply this to any distribution where we have a theoretical reason to expect a certain result.  E.g., with two dice, each with six sides.  What results are possible and what likelihood do we have?

  1.  
  2.   *               Snake-eyes!
  3.   **             (1 and 2; 2 and 1)
  4.   ***           (1 and 3; 3 and 1; 2 and 2)
  5.   ****         (1 and 4; 4 and 1; 3 and 2; 2 and 3)
  6.   *****       (1 and 5;  5 and 1; 4 and 2;  2 and 4; 3 and 3)
  7.   ******      (4 and 3;  3 and 4;  5 and 2;  2 and 5; 6 and 1; 1 and 6)
  8.   *****       (4 and 4; 5 and 3; 3 and 5; 6 and 2; 2 and 6)
  9.   ****         (5 and 4;  4 and 5; 6 and 3;  3 and 6)
  10.   ***            (5 and 5; 6 and 4; 4 and 6)
  11.   **              (6 and 5; 5 and 6)
  12.  *                  Boxcars!
Suppose we try real dice 36 times and see what we get:

Total
Expected
Observed
2
1

3
2

4
3

5
4

6
5

7
6

8
5

9
4

10
3

11
2

12
1


We can compute the chisquare with Graph Pad QuickCalcs on the Internet. 
We will then apply the same statistic to crosstabulations where the expected frequencies are determined by the marginal frequencies.  Last class we calculated expected frequencies, see the notes below.:

For a criminal justice example, consider the study of racial profiling by the San Diego police

February 1:  We will go over the examples on pages 47-53 in the Workbook, as well as Exercise 2b. 

We will also introduce the concept of Expected Frequencies.  For this purpose we will use a simple 2 by 2 distribution as follows.  The variables are gender and opinion on an issue, each of which has two values:

25 men agreed
17 men disagreed
65 women agreed
30 women disagreed
 
 

Observed Frequencies or Obtained Frequencies Men Women total
Agree 25 65 90
disagree 17 30
47
total 42 95
137

    We can compute expected frequencies, based on the null hypothesis that men and women do not differ intheir opinions.  We can compute these knowing only the marginal or total frequencies.  The easy way to compute them is to multiple the row total for each cell by the column total for that cell, then divide by the grand total.  Another way would be to convert the row totals to proportions, then multiply then by the column totals.  Expected Frequencies - rt *ct /gt

 
Expected Frequencies  men women total
agree 90*42/137=27.59 90*95/137=62.41 90
disagree 47*42/137=14.41 47*95/137=32.59 47
total 42 95
137

  What would we get if we used the expected frequencies to make acolumn percentage table?  The percentages would be the

January 27:  We spent most of the class on descriptive statistics.  The required reading is on the Internet and will be distributed in class on February 1.  You should know how to do frequency distributions and how to calculate means and standard deviations exactly as explained in the reading.  (Do not group values together as we did in class).  There are mean and standard deviation items at the end of the Percents and Expected Frequencies quiz, which is now open.

January 25:
How does social science differ from other ways of thinking:  poetry, philosophy, theology, physical or biological sciences, history, journalism?  How would we divide up fields of study?  Physical Science,  Social Science, Humanities?  Science, Art and Morality? Or, in Greek, Episteme, Techne, PhronesisThree approaches to knowledge. At Rutgers Camden we divide knowledge up differently:  Rutgers Camden requirements.  How does social science differ from the other categories?  Some sociologists like to think of us as a science similar to chemistry or physics, others see us as closer to history or journalism.  The latter conceptions might make us exempt from human subjects regulations, if we are not doing research aimed as generalization.  But we do not want to give up the hope of establishing generalizations.

Social science begins with concepts as do other fields such as  philosophy and even mathematics if we recognize that numbers are concepts.  The small integers are especially important, especially Zero and One (or nothing and something).  Religion may also start with concepts  The Bible says In the beginning there was the Word, and the Word was with God, and the Word was God What does that mean?  Ask a theologian.  Religious concepts are good if they provoke spiritual reflection, as in reciting a Mantra in Buddhism.  Literary concepts are good if they are beautiful, which social sciences seldom are.   W.H. Auden's poem Under Which Lyre is  an aesthetic attack on social science and other applied sciences.  Social science may not appeal to poets, but it can provide objective evidence of important points.  Florence Nightingale used social research to advocate for better nursing care in the British armed forces during the Boer War.  She invented the bar graph and pie chart.  Felton Earls and his colleagues used a combination of research methods to study the causes of urban crime.  Their organizing concept was "collective efficacy".

 In Social Science, a concept is good if it helps us to understand empirical reality.  A good concept leads to useful generalizations or theories.  Theories are general statements about relationships between concepts that reflect how people think and behave.  It can also be operationalized which means finding indicators to measure it.  A very common way of operationalizing a concept is to write a survey question.  Others may be operationalized by observation or by physical measurement or by counting things.  In criminal justice, concepts are often operationalized by having police officers fill out reports on incidents.  We can find a good list of sociological concepts by going to survey research archives, where concepts are translated into survey questions.  Check the General Social Survey and the Eagleton poll.Criminal justice concepts can be found on the  Bureau of Justice Statistics WEB site.
  There are also bad concepts.   For an example of one I think is bad, click on virtropy.  What's wrong with this concept?  Recently there has been some controversy over "race" as a concept.  Some people say races do not "really" exist.  Biologically, that is true if by "exist" you mean that people fall into distinct categories.  Physical differences exist with regard to skin color and other traits, but they are distributed continuously, not in distinct categories.  Sociologically, racial differences exist and are important.  The people who say they do not "exist" are usually in favor of using them for affirmative action programs, or even for reparations, so they concede that they have sociological meaning.  That meaning differs from society to society, and may change over time.  The growth of the Hispanic population in the US is forcing a change in how we think about this. Census Racial Categories.    Census Document on Racial and Ethnic CategoriesRacial categories in Latin America.   Other concepts we can consider are: poverty, power, crime, murder, race, IQ, liberalism/conservatism, homelessness. Or we could look at Personality Types as defined by Carl Jung and Measured by Isabel Meyers-Briggs

January 20: 

We began with the Microcase software.  If you miss class today, you should work through pages 1 to 11 in the Workbook on your own. 
Computation of percentages.  A percent is calculated on a given base   In a cross-tabulation the base can be the row total, the column total or the grand total.   To get the percents, you first put the percents in a two by two table.  Then you compute the row, column and grand totals.  Then you use the totals as the base to compute the appropriate percent.

                   Male    Female   -    total observed frequencies

  Agree         55           79         134

   Disagree    89            47        136
 
totals            144          126       270


   ____ % OF THE MEN AGREED      number of men who agreed/the number of men * 100 ;  55/144 * 100  38.2%  

   ____% OF THE WOMEN AGREED    79/126 *100   =  62.7%

_____ % OF THE PEOPLE WHO AGREED WERE MEN       number of men who agreed/the number of people who agreed * 100  55/134  41.0%

 _____ % OF THE RESPONDENTS WERE AGREEABLE MEN    number of men who agreed/the number of respondents * 100  55/270*100  20.4%



January 18:  We went over the syllabus , schedule and assignments pageenrolling assignment, and the use of WEBCT.  All "quizzes" should be taken for the first time at least two days before they are due.  No allowance will be made for technical difficulties if you wait until the last day to try the quiz.   Please remember to sign the attendance sheet each day.  I allow three missed classes for good reasons such as illness and funerals.  It is not necessary to bring excuses until your excused absences exceed three.  Students who add the class late and miss the first class or two have used up some of their excused absences and are responsible for completing all assignments on time.