There were 821 subjects enrolled in this study. Of the 414 randomized to the treatment (Hydroxychloroquine) arm, 49 (11.8%) developed Covid (or probable Covid) within 14 days of randomization. Of the 407 randomized to the placebo arm, 58 (14.3%) developed Covid (or probable Covid) within 14 days of randomization.

In Homework #3, you reported a sample relative risk of developing COVID for the Hydroxychloroquine group compared to the placebo group of 0.83 with a 95% CI of 0.58 to 1.19.

21: Suppose you plan to perform a chi-square (or two sample z-test, or Fisher's Exact Test) for this study. What is the null hypothesis for this test in terms of the Risk Difference (RD)?

a. RD=1

b. RD not equal to 1

c. RD = 0

d. RD not equal to 0

22: Suppose you plan to perform a chi-square (or two sample z-test, or Fisher's Exact Test) for this study. What is the null hypothesis for this test in terms of the Relative Risk (RR)?

a. RR=1

b. RR not equal to 1

c. RR = 0

d. RR not equal to 0

23: Suppose you plan to perform a chi-square (or two sample z-test, or Fisher's Exact Test) for this study. What is the null hypothesis for this test in terms of the Odds Ratio (OR)?

a. OR = 1

b. OR not equal to 1

c. OR = 0

d. OR not equal to 0

24: Based on the resulting confidence interval for the relative risk only, what can you ascertain about the p-value from the hypothesis test for Questions 21-23?

a. As the 95% CI for the relative risk includes 0, the p-value is greater than 0.05.

b. As the 95% CI for the relative risk does not include 0, the p-value is less than 0.05.

c. As the 95% CI for the relative risk includes 1, the p-value is greater than 0.05.

d. As the 95% CI for the relative risk does not include 1, the p-value is less than 0.05.

26.

The p-value from a chi-square test was 0.31. What is the interpretation of this p-value (i.e., what probability does this p-value quantify)?

a. The probability of getting a sample result (for example a relative risk of 0.83) as extreme or more extreme (as far or farther from the null value) if the alternative hypothesis is true is 0.31

b. The probability of getting a sample result (for example a relative risk of 0.83) as extreme or more extreme (as far or farther from the null value) if the null hypothesis is true is 0.31.

c. The probability that the null hypothesis is true is 0.31.

d. The probability that the alternative hypothesis is true is 0.69.

27: Assuming an alpha level of 0.05, what decision should the researchers make based on the p-value from Question 26?

a. The researchers should "fail to reject the null hypothesis".

b. The researchers should "reject the null hypothesis".

c. The researchers should question whether the study was well designed because of this p-value.

d. The researchers should feel confident that the study results are valid.