4.1.2标准正态分布:对于一般正态分布p58 1=2 (a) (c) Fig 4-2 (a)Different means, same variance; (b same mean, different 4-6 variances;(c)different means, different variances4-6 4.1.2 标准正态分布：对于一般正态分布p58 Fig 4-2 (a) Different means, same variance; (b) same mean, different variances; (c) different means, different variances