How to perform test of Normality Data with STATA
In Stata, you can test normality by either graphical or numerical methods. The former include drawing a stem-and-leaf plot, scatterplot, box-plot, histogram, probability-probability (P-P) plot, and quantile-quantile (Q-Q) plot. The latter involve computing the Shapiro-Wilk, Shapiro-Francia, and Skewness/Kurtosis tests.
The examples below are for the variable
score
:Graphical methods | |
---|---|
Command | Plot drawn |
. stem score | stem-and-leaf |
. dotplot score | scatterplot |
. graph box score | box-plot |
. histogram score | histogram |
. pnorm score | P-P plot |
. qnorm score | Q-Q plot |
Numerical methods | |
---|---|
Command | Test conducted |
. swilk score | Shapiro-Wilk |
. sfrancia score | Shapiro-Francia |
. sktest score | Skewness/Kurtosis |
Be aware that in these tests, the null hypothesis states that the variable is normally distributed. That means the data is considered normal if > 0.05
good luck
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