单项选择题
A.z0.05B.z0.025C.±t0.05(n1+n2-2)D.±t0.025(n1+n2-2)
A.z0.05B.z0.025C.t0.05(n-1)D.t0.025(n-1)
A.μ〉μμB.μ≠μμC.μ〈μμD.不确定