There are some tests that can be used to assess whether our assumption of homoskedasticity holds or not. One of them is the Breusch-Pagan/Cook-Weisberg test of heteroskedasticity (estat hettest command). It uses the fitted values of the y-variable and produces a p-value: if p<0.05, it means that our assumption is violated.

More information help estat hettest

Practical example

The first step is re-run the multiple linear regression model. The quietly option is included in the beginning of the command to suppress the output.

quietly reg gpa cognitive bullied ib1.skipped if pop_linear==1

Then we run the test.

estat hettest

Since the p-value is above 0.05 (0.0884), we can conclude that our model does not have problems with heteroskedasticity.