Unit 10 Exercises (Independent Proportions)

(10.1) SMOKING: A school-based survey shows the following data on the prevalence of smoking in boys and girls:

(A) Report the prevalence of smoking in girls and the prevalence of smoking of boys. How do they compare?
(B) Then test whether there is a significant difference in these prevalences. Let a = .05. Show all calculations, and report all hypothesis testing steps.

(10.2) RESTENOSIS: Each year cardiologists open clogged coronary arteries only to have many of these same arteries re-narrow again following surgery. (Narrowing of an artery is called "stenosis," and re-narrowing "restenosis.") A study sponsored by the National Institutes of Health was performed to help determine whether infection with a common virus, cytomegalovirus (CMV), was predictive of the re-growth of arterial plaque (Zhou et al., 1996). Data were:

(A) Report the incidence of restenosis in the CMV+ group and CMV- group. How do these compare?
(B) Test to see if the association between CMV infection and restenosis is significant. Show all calculations and all hypothesis testing steps.
(C) In plain language, discuss the implications of the above statistical results. Do they support the theory that a viral infection with CMV plays a role in arteriosclerosis?

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