**Standard Normal Distribution 標準常態分配**

The **standard normal distribution** has a bell-shaped density with mean
and standard deviation

The standard normal distribution is denoted by *N*(0,1) or *Z*.

- 1.
- 2.

標準常態分配的值可以由查標準常態分配表得知.

- 例
- Find
.

The two events [*Z*<-1.9] and [*Z*>2.1] are incompatible, so we add their probabilities: . As indicated in follow,*P*[*Z*>2.1] is the area to the right of 2.1, which is . The normal table gives*P*[*Z*<-1.9]=.0287 directly. Adding these two quantities, we get