Some multiple choice questions:
1. Quota sampling: a. is a form of random sampling
b. is a form of convenience sampling.
2. A two-step process in which census tracts or other
small geographic units are sampled, then the samples of individuals are
selected from within each aggregate is called: a. simple random sampling
b. stratified sampling c. quota sampling
d. cluster sampling e. snowball sampling
3. The range within which we estimate the statistic to
depart from the parameter is known as the: a. margin
of error b. confidence level c. confidence interval d.
confidence game
4. If all members of the population have an equal chance
of being in our sample, we have a: a. simple random sample b.
systematic sample c. stratified sample d. quota sample e.
cluster sample
5. If we draw samples of neighborhoods, then choose randomly
within the selected neighborhoods we have a: a. simple random
sample b. systematic sample c. stratified sample d. quota
sample e. cluster sample
Statistical questions. Instructions for answering these questions are in the Guide to Computing Margins of Error. In these items, the phrase "margin of error" refers to a 95% confidence interval or two standard errors. This can be represented as + or - a certain amount.
1. In a college class with 85 students, 42 of whom are Hispanic, the mean on the midterm was 75. The mean for the Hispanics was 77, that for the non-Hispanics was 73. In all cases, the standard deviation was 5. What is the margin of error for the mean score for the Hispanic students? For the non-Hispanic students?
2. A researcher wants to obtain a margin of error of no more than 2% in a survey of a county with a population of 300,000. How large a sample is needed?
3. 15% of the respondents in a survey of a South Jersey voters favored increasing the state sales tax to cover the budget deficit. 70% opposed the proposal and the remainder were undecided. There were 625 respondents. What is the margin of error for the percent favoring the proposal? For the percent opposed? For the percent undecided?
4. In a survey of 1000 voters, 600 were Democrats, 300 Republicans and 100 Libertarian. 25% of favored sending both the Israelis and Palestinians to Australia and turning the empty territory over to the Kurds. What is the margin of error for this percentage?
6. A survey is to be conducted of attitudes among white, black and hispanic respondents in Camden County. The population is 300,000. Of this population, 80% is white, 15% is black and 4% is Hispanic. The researcher wants to achieve a 5% margin of error for the estimates for each of the groups. How large a sample is needed?
7. In a survey of community residents, the mean income was $18,745 with a standard deviation of $1,845. There are 370,000 residents in the community. 1000 were sampled in the survey. What is the margin of error for this mean score?
8. A survey of the tri-county area has 3568 respondents, of whom 80% are white (and not Hispanic), 12% are black, 3% Hispanic and 5% "other". What is the margin of error for statistics about the opinion of the hispanic residents? Of the black residents? Of the non-Hispanic whites?
9. What is the margin of error for statistics based on the responses of all the respondents in the survey above?
10. A study of traffic speeds on the New Jersey turnpike showed that the average speed in a 65 mph zone was 78 mph, with a standard deviation of 3 mph. 25,000 cars were measured by an automatic device. What is the margin of error for the estimated speed?