In this study, the outcome of interest was the change in women's responses on the Hamilton Depression Rating Scale between the treatment (antidepressant + oral creatinine supplementation) and control (antidepressant + oral placebo supplementation)

Because of randomization, the Hamilton Depression Rating Scales (HSRD) were nearly identical on average between the treatment and control groups. As such, the Hamilton scores at the end of the eight-week follow-up period can be compared to assess differences, if any, in the average Hamilton Score change.

Summary statistics about the resulting Hamilton Depression Rating Scale (HDRS) scores at the end of the eight-week clinical trial are as follow:

Group	n	Mean	Standard Deviation
Treatment	17	5.4	3.0
Control	22	9.8	3.5

In Homework #3, you reported sample mean difference in Hamilton Score changes between the Treated and Control groups of -4.4, with a 95% CI of (-6.5 to -2.3). To compute this confidence interval, you also computed the standard error of this mean difference:

SE^(xtrtxcontrol)=3.0217+3.52221.04^()=3.0217+3.52221.04

Suppose you plan to perform a two-sample t-test for this study. What is the null hypothesis for this test?

a. The mean HDRS scores are different in the treatment and control populations

b. The mean difference in HDRS scores between the treatment and control populations is 1.

c. The mean HDRS scores are equal in the treatment and control populations.

d. The mean difference in HDRS scores between the treatment and control populations is not 0.