What is the null hypothesis when comparing two group means in a trial?

What is the null hypothesis when comparing two group means in a trial?

• A. The null hypothesis states there will be a difference between the groups.
• B. The null hypothesis asserts the experimental treatment is superior.
• C. The null hypothesis asserts there is no difference between the experimental and control group means.
• D. The null hypothesis is not applicable in randomized trials.

Answer: (C)

When comparing two group means, the starting assumption is that the groups are the same on average—that there is no difference between the means. This is the null hypothesis: there is no difference between the experimental and control group means. The purpose of the test is to see whether the observed data provide enough evidence to reject that assumption in favor of an alternative that there is a difference (the alternative can be two-sided or one-sided, depending on the hypothesis). The other statements describe the alternative (a difference exists, or that the treatment is superior) or misstate applicability in randomized trials, which is not correct because hypothesis testing of mean differences is exactly what randomized trials are designed to do.

When comparing two group means, the starting assumption is that the groups are the same on average—that there is no difference between the means. This is the null hypothesis: there is no difference between the experimental and control group means. The purpose of the test is to see whether the observed data provide enough evidence to reject that assumption in favor of an alternative that there is a difference (the alternative can be two-sided or one-sided, depending on the hypothesis). The other statements describe the alternative (a difference exists, or that the treatment is superior) or misstate applicability in randomized trials, which is not correct because hypothesis testing of mean differences is exactly what randomized trials are designed to do.