題組內容

一、(50%)
5. (10%, 5% each) Let X̄, Ȳ, S²x and S²y be the respective sample means and unbiased estimates of the variances obtained from independent samples of sizes n and m from the normal distributions N(μx, σ²x) and N(μy, σ²y), where μx, μy, σ²x, σ²y are unknown. If the sample sizes n and m are smaller than 30, construct (1 - α)100% confidence interval for μx - μy when



a. two population standard deviations can be assumed equal.