A.兩總體均數(shù)相等 B.兩總體均數(shù)不等 C.差值的總體均數(shù)等于0 D.差值的總體均數(shù)不等于0 E.樣本的總體均數(shù)與已知的總體均數(shù)相等
A.CV B.s C.s D.R E.t