One of the key assumptions of the ordinary regression model is that the errors have the same variance throughout ... Autocorrelated Time Series"; proc gplot data=a; symbol1 v=dot i=join; symbol2 ...

data out; set out; shat = sqrt( vhat ); run; title "Predicted and Actual Standard Deviations"; proc gplot data=out; plot s*time=1 shat ... from a constant unconditional variance. The data generating ...