Due: by Monday December 10, 2012 @ 8 AM (no exceptions)
Please submit your assignment via Blackboard.
Material Covered: Chapters 8, 9
Instructions: For each question that you wish to receive credit for, please show all of your work and make sure that
you answer each problem completely in your own words. Please type your solutions (or write them neatly on separate
paper and scan them to create a pdf or comparable file). You may use StatCrunch (statcrunch.american. edu
Password: eagle
The extra credit earned will go towards your Exam grades. A complete and correct answer for each part
will earn you the number of points indicated next to the question. You may submit responses to one, two,
three or all parts.
1. (1 point) From our text: p. 508: 8.92
In a random sample of 975 students from a large public university , it was found that 463 of the students changed
majors during their college years.
(a) Give a 95% confidence interval for the proportion of students at this university who changed majors
(b) Express your results from (a) in terms of the percent of students who change majors
(c) University officals concerned with counseling students are interested in the number of students who change
majors rather than the proportion. The university has 37,500 undergraduate students. Convert the confidence
interval you found in (a) to a confidence interval for the number of students who change majors during their
college years
2. ( 1 point) From our text: p. 508: 8.93
Go the gallup poll web site gallup.com and final a poll that has several questions of intrest to you. Summarize the
results of the poll giving margins of error and comparisons of interest(for this exercise you may assume that the
data comes from an SRS)
3. (2 points) Please review “20 Questions A Journalist Should Ask About Poll Results” presented by NCPP
(the National Council on Public Polls). For the poll that you selected for #2 please address at least five of
the given questions.
4. (2 points) “In a study of eating disorders in female adolescents, Gross (1985) asked each of her participants whether
they would prefer to gain weight, lose weight, or maintain their current weight. (Note: Only 12% of the girls in
Gross’s sample were actually more than 15% above what normative tables say they should weigh, a common cutoff
for a label of “overweight.”) When she broke down the data for girls by race (African-American versus white), she
obtained the following results. (Other races have been omitted because of the small sample sizes.)
Reducers
Maintainers Gainers
Total
White
352
152
31
535
African-American
47
28
24
99
Total
399
180
55
634
From Fundamental Statistics for the Behavioral Sciences, 6th ed by David C. Howell
a) Calculate the appropriate conditional distributions.
b) State an appropriate set of hypotheses, and find the value of the χ2 statistic here and its P-value.
c) What conclusions can you make based on your work from a and b?