Determining Approximate Sample Size for Independent Samples
A prominent football coach asserted that football players are getting bigger
all of the time. A sportswriter for a newspaper wanted to determine the
validity of this statement by comparing a sample of NFL football players
competing today versus a sample of professional players competing 10 years
ago. He decided to adopt alpha = .05 and beta = .05 (or power equal to
.95).
If the difference between the body weight of professional players today
versus those 10 years ago was as great as 15 pounds, he would like to know
it. A pilot study of body weights from football players who completed both
years suggested that the standard deviation was approximately 20 pounds
for each sample. What should be the size of the sample to test the hypothesis?
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