G12.10

Sample size requirement.A variable has a standard deviation of 40 mg/dL. We want to test a mean difference in two groups with alpha=0.05 (two-sided) and power=80%.

1. How many observations are needed to detect a difference of 10 mg/dL with equally sized groups?

1. Suppose we can only recruit 150 subjects into group 1. How many are needed in group 2?