The plot of residuals by the predicted values shows that the variance of the errors increases with increasing predicted polishing time. There is, otherwise, good scatter.

To check the residuals by the diameter, recall the Simple Scatterplot dialog box.

Deselect time as the y variable and select Standardized Residual as the y variable.

Click OK.

The plot of residuals by diameter shows the same results. To correct the heteroscedasticity in the residuals in further analyses, you should define a weighting variable based on the inverse of the diameter of the product. Using the weighting variable will decrease the influence of products with large diameters and highly variable polishing times, resulting in more precise regression estimates.