Plasma glucose levels are used to determine the presence of diabetes. Suppose the mean in (plasma-glucose) concentration (mg/dL) in 35-44 year olds is 4.86 with standard deviation = 0.54. A study of 100 sedentary people in this age group is planned to test whether they have a higher or lower level of plasma glucose then the general population.
If the expected difference is 0.10 units, then what is the power of such a study if a two-sided test is to be used with a=.05. How many people would need to be studied to have 80% power under these assumptions?