Checking the normality of data variables

You get separate results for each variable in univariate tests and plots .

For multivariate tests and plots, combined results for all variables are displayed against each test.

In normality test, we assume the null hypothesis that the data follows normal distribution.

If p-value is less than 0.05, then the normality assumption is rejected.

Q-Q plot

If the points in the plot for variables follow a straight line, then the data follows normality.

Histogram

If the distribution curve of the data in a histogram approximately matches the normal distribution curve, then data is normally distributed.

Box plot

A box plot that is symmetric with the median line at approximately the centre of the box and with symmetric whiskers indicate that the data might have come from a normal distribution.

Chi square Q-Q plot

If the Chi Square distribution resembles a straight line for data, then the data follows a normal distribution.

Perspective plot and contour plot

For bivariate normally distributed data, we obtain a three-dimensional bell-shaped graph from the perspective plot and we can observe a similar pattern in the contour plot also.