Recently it has been observed that HIV-infected patients develop peripheral lypo

Question

Recently it has been observed that HIV-infected patients develop peripheral lypoatrophy while on potent antiretroviral therapy. A clinical trial is planned to determine whether a new chemical will improve this condition. In the trial, participants will be randomized to receive the new chemical or a placebo, and changes from baseline in subcutaneous adipose cross-sectional area as measured by CT scan will be calculated after 24 weeks of treatment. Investigators hope to show that the increases in patient receiving the chemical will be greater than the increases in patient receiving the placebo. The hypothesize that the participants assigned to the chemical arm will exhibit a mean change of 30% and that the participants assigned to the placebo arm will exhbit a mean change of 0%. Prior literature suggests that the standard deviation of the changes will be 57% in both arms. How many participants are needed to ensure 80% power? Assume that a=0.05, that there are equal number in each group, and that 20% participants will drop out over the course of follow-up.

Explanation / Answer

The larger your sample size is, the more chance it has to reflect the actual population mean. By doing so, there is also an increased chance for your data to have statistical significance. If you use a good amount of participants for your research, there is a smaller margin or error as well as standard deviation. There are also less outliers than would be in a smaller sample size.

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