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Heteroscedasticity, the non-constant variance of residuals in regression analysis, can undermine the validity of standard inference and lead to inefficient or biased parameter estimates. Classical ...

One of the key assumptions of the ordinary regression model is that the errors have the same variance throughout the sample. This is also called the homoscedasticity ...

The SPEC option performs a model specification test. The null hypothesis for this test maintains that the errors are homoscedastic, independent of the regressors and that several technical assumptions ...