The mean sd of ln [calcium intake (mg)] among 25 females, 12 to 14 years of age, below the poverty level is . Similarly, the mean sd of ln [calcium intake (mg)] among 40 females, 12 to 14 years of age, above the poverty level is .
1 Test for a significant difference between the variances of the two groups.
2 What is the appropriate procedure to test for a significant difference in means between the two groups?
3 Implement the procedure in Problem 2 using the critical-value method.
4 What is the p-value corresponding to your answer to Problem 3?
5 Compute a 95% CI for the difference in means between the two groups.
6 Suppose an equal number of 12- to 14-year-old girls below and above the poverty level are recruited to study differences in calcium intake. How many girls should be recruited to have an 90% chance of detecting a significant difference using a two-sided test with ?
7 Answer Problem 6 if a one-sided rather than a two- sided test is used.
8 Using a two-sided test with , answer Problem 6, anticipating that two girls above the poverty level will be recruited for every one girl below the poverty level who is recruited.
9 Suppose 50 girls above the poverty level and 50 girls below the poverty level are recruited for the study. How much power will the study have of finding a significant difference using a two-sided test with , assuming that the population parameters are the same as the sample estimates in Problem 1?
The drug diflunisal is used to treat mild to moderate pain due to osteoarthritis (OA) and rheumatoid arthritis (RA). The ocular effects of diflunisal had not been considered until a study was conducted on its effect on intraocular pressure in glaucoma patients who were already receiving maximum therapy for glaucoma.
10 Suppose the change in intraocular pressure after administration of diflunisal (follow-up – baseline) among 10 patients whose standard therapy was methazolamide and topical glaucoma medications was mm Hg. Assess the statistical significance of the results.
11 The change in intraocular pressure after administration of diflunisal among 30 patients whose standard therapy was topical drugs only was mm Hg. Assess the statistical significance of these results.
12 Compute 95% CIs for the mean change in pressure in each of the two groups identified in Problems 10 and 11.
13 Compare the mean change in intraocular pressure in the two groups identified in Problems 10 and 11 using hypothesis-testing methods.