10.31 Do a larger proportion of college students than young children eat cereal? Researchers surveyed
both age groups to find the answer. The results are shown in the table below. (a) State the hypotheses
used to answer the question. (b) Using α = .05, state the decision rule and sketch it.
(c) Find the sample proportions and z statistic. (d) Make a decision. (e) Find the p-value and
interpret it. (f ) Is the normality assumption fulfilled? Explain.
College Students Young Children
Statistic (ages 18-25) (ages 6-11)
Number who eat cereal x1 = 833 x2 = 692
Number surveyed n1 = 850 n2 = 740
10.47 Has the cost to outsource a standard employee background check changed from 2005 to 2006? A
random sample of 10 companies in spring 2005 showed a sample average of $105 with a sample
standard deviation equal to $32. A random sample of 10 different companies in spring 2006
resulted in a sample average of $75 with a sample standard deviation equal to $45. (a) Conduct a
hypothesis test to test the difference in sample means with a level of significance equal to .05.
Assume the population variances are not equal. (b) Discuss why a paired sample design might
have made more sense in this case.
10.64 A cognitive retraining clinic assists outpatient victims of head injury, anoxia, or other conditions
that result in cognitive impairment. Each incoming patient is evaluated to establish an appropriate
treatment program and estimated length of stay. To see if the evaluation teams are consistent,
12 randomly chosen patients are separately evaluated by two expert teams (A and B) as shown. At
the .10 level of significance, are the evaluator teams consistent in their estimates? State your
hypotheses and show all steps clearly. LengthStay
Estimated Length of Stay in Weeks
Team 1 2 3 4 5 6 7 8 9 10 11 12
A 24 24 52 30 40 30 18 30 18 40 24 12
B 24 20 52 36 36 36 24 36 16 52 24 16
The solution uses ANOVA and nonparametric parameters to determine if college students or young children eat more cereal.