Question

設隨機變量ξ服從標準正態分布N(0,1),已知Φ(-1.96)=0.025,則P(|ξ|＜1.96)等于

A.0.025                B.0.050                C.0.950               D.0.975

Answer 1

C  ∵ξ～N(0,1),∴正態密度曲線關于y軸對稱.

又∵Φ(-1.96)=0.025,∴Φ(|ξ|＜1.96)=1-2×0.025=0.950.