- Sample size justification: The sample size requirement was determined based on the ability to detect a HbA1c reduction of at least 0.4 units, significance of the test (α) of 0.05, β of 2 and power (1-β) of 0.80 (The FDA criterion for drug effectiveness is a HbA1c reduction of 0.3 to 0.4 units). Examination of recent study results for HbA1c of the research group on type 2 diabetic subjects indicated a standard deviation of 0.32. So the desired total number to complete this study is N=80, or 120 enrolled assuming a 30% attrition rate.