Question

A clinical trial is being conducted in order to determine the efficacy of a new drug that will be used to treat
rheumatoid arthritis. The efficacy of the medication will not only be determined by the physical improvement of
symptoms but will also be determined by using a blood test to examine the concentration of C-reactive protein (an
inflammatory marker) in an individual's blood. If the researcher wants a margin of error for the level of C-reactive
protein to be less than or equal to 2.0 mg/dL and if the standard deviation for C-reactive protein concentrations
among arthritis patients was previously documented at 7 mg/dL, how many patients should be recruited for each
group of individuals in the study, assuming a 95% confidence interval will be used to quantify the mean differences
between the control group and the treatment group?

Answer 1

The following information has been provided:

The critical value for the significance level α=0.05 is zc​=1.96. The following formula is used to compute the minimum sample size required to estimate the population mean μ within the required margin of error:

Therefore, the sample size needed to satisfy the condition , and it must be an integer number, we conclude that the minimum required sample size is

Please let me know in comments in case anything is unclear. Will reply ASAP. Do upvote if satisfied!