Reference Suppose that n measurements are to be taken under a treatment condi...

Reference

Suppose that n measurements are to be taken under a treatment condition and another n measurements are to be taken independently under a control condition. It is thought that the standard deviation of a single observation is about 10 under both conditions. How large should n be so that a 95% confidence interval for μ_X −μ_Y has a width of 2? Use the normal distribution rather than the t distribution, since n will turn out to be rather large.