Suppose we are planning an exercise trial in 50–74-year-old men, to see if a daily exercise regime for a year will lead to improved quality of life compared to a control group. We know from published data on the SF-36 quality of life measure that at this age men have a mean score on the Physical Function dimension of 73.0, with a standard deviation of 27.0.

Suppose the effect of the daily exercise regime on physical function will be considered important if it increases the Physical Function Dimension of the SF-36 by at least 10 points. How many patients would be needed for a two-sided signifi cance of 5% and 90% power?