Suppose that n measurements are to be taken under a treatmen

Suppose that n measurements are to be taken under a treatment condition (X) and another 3n measurements are to be taken independently under a control condition (Y ). It is thought that the standard deviation of a single observation is about 5 under both conditions. How large n be so that a 95% confidence interval for µX µY has a width of 4? Here µX and µY are the population means of X and Y , respectively.

Solution