If you wish to turn the assignment in in class, print it out and write the answers on the sheet.  If you wish to submit it to WEBCT, type your answers in the file,.save it in html format and submit it by the deadline.  Instructions for answering these questions are in the Guide to Computing Margins of Error.

Answer the following items on this page.  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 125 students, 32 of whom are black, the mean on the midterm was 75. The standard deviation was 8. What is the margin of error for this mean?

2. A researcher wants to obtain a margin of error of no more than 5% in a survey of a county with a population of 300,000. How large a sample is needed?

3. 55% of the respondents in a survey of a state with seven million Republican voters voted for Bush, 45% for Gore. There were 625 respondents. What is the margin of error for the percent voting for Bush?

4. What is the margin of error for the Gore vote?

5. In a survey of 1000 voters, 600 were Democrats, 300 Republicans and 100 Libertarian. 65% of the Republicans favored George Bush in the primary. 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 3% 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 $28,745 with a standard deviation of $2,345. 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. In a survey of Camden County residents, 55% were in favor of a proposal to abolish traffic circles. There are 300,000 county residents, of whom 1200 were sampled. What is the margin of error on this percentage?

9. A survey of the tri-county area has 356 respondents, of whom 82 are black and 65 hispanic. What is the margin of error for statistics about the opinion of the hispanic residents?

10. What is the margin of error for statistics based on the responses of all the respondents?

11. In a survey of Rutgers students, 250 white students were sampled and 117 black students. 83% of the students said that Methods and Techniques of Social Research was the most useful class they ever had. What is the margin of error for this percentage?

12. 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?