15. An Arthritis Drug To determine the effectiveness of a drug for arthritis, a researcher studied two groups of 200 arthritic patients. One group was inoculated with the drug; the other received a placebo (an inoculation that appears to contain the drug but actually is nonactive).

After a period of time, each person in the study was asked to state whether his or her arthritic condition had improved.

You want to know whether these data indicate that the drug was effective in improving the condition of arthritic patients.

a. Use the chi-square test of homogeneity to compare the proportions improved in the populations of treated and untreated subjects. Test at the 5% level of significance.

b. Test the equality of the two binomial proportions using the two-sample z-test of Section 9.5. Verify that the squared value of the test statistic z2 5X2 from part

a. Are your conclusions the same as in part a?

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Treated Untreated Improved Not Improved 117 74 83 126