6.4 Assessing normality; normal Probability Plots
The normal probability plot is a graphical technique to identify substantive departures from normality
即如果sample满足正态分布，则1-12位置上对应的y值应该为这一列上的值
Noted：
之前统计正态分布时需要由直方图过渡到正态曲线，横坐标是每一类，在这里是样本本身。
由table3一一对应，作图：
根据以上rule判断正态情况。
Note: If two or more observations in a sample are equal,you can think of them as slightly different from one another for purposes of obtaining their normal scores.
如图，可将normal-score值改为对应的percentage
A probability or percent scale is used instead of normal scores
Detecting Outliers with normal Probability Plots
a去掉outlier得到b
由此判断该数据为正态分布
