Arandom sample of 21 students in school a yielded a mean of x1 = 72 and a variance of s 2 1 = 16 for scores on a college placement test in mathematics. another random sample of 16 students in school b yielded a mean of x2 = 70 and a variance of s 2 2 = 20 for scores on a college placement test in mathematics. assuming the scores to be normally distributed, construct a 98% confidence interval for σ 2 1/σ2 2 .