As I explain in Chapter 6, a critical assumption of the
classical linear regression model is homoskedasticity — that
the variance of the error term is constant over various values
of the independent variables. However, this assumption may
not always hold. When it doesn’t happen, you have
heteroskedasticity. This chapter shows you how to determine
whether you have heteroskedasticity in a particular
application and what you can do to remedy it if you do.