The weighted least squares (WLS) technique
transforms the original (heteroskedastic) model into a
homoskedastic one by using information about the nature of
the heteroskedasticity. The goal of the WLS transformation is
to make the error term in the original econometric model
homoskedastic. First, you assume that the heteroskedasticity
is determined proportionally from some function of the
independent variables. Then you use knowledge of this
relationship to divide both sides of the original model by the
component of heteroskedasticity that give the error term a
constant variance