Suppose you are planning an experiment to test the effects of various diets on the weight gain of young turkeys. The observed variable will be Y = weight gain in 3 weeks (measured over a period starting 1 week after hatching and ending 3 weeks later). Previous experiments suggest that the standard deviation of Y under a standard diet is approximately 80 g. 23 Using this as a guess of σ, determine how many turkeys you should have in a treatment group, if you want the standard error of the group mean to be no more than
(a) 20 g
(b) 15 g