An Investigator Wants to Compare Mean HbA1c Levels Among Three

Essay

An investigator wants to compare mean HbA1c levels among three groups.
a. Suppose that the three groups being compared involve a control and two experimental therapies. The purpose of the study is exploratory to see if the therapies impact HbA1c. The investigator uses the Bonferroni adjustment to reduce the chance of making a type 1 error. Is this appropriate? What are the implications of making the adjustment?
b. Suppose that the study is an observational one and is the first investigation of differences in HbA1c for these three groups. The purpose of the study is exploratory to see if a clinical trial investigating these three groups is warranted. Without adjusting for multiple comparisons, the investigator finds that there is a difference between groups 1 and 2, but after adjusting for multiple comparisons, the p-value is no longer significant. Advise the investigator.
c. Suppose that the study is a confirmatory clinical trial to investigate the impact of a no-treatment control, an active control, and a treatment on HbA1c. When making comparisons among the three groups, the investigator decides to implement an adjustment to protect against making a type 1 error. Is this appropriate? What are the implications of making the adjustment?