To check for influential points, recall the Simple Scatterplot dialog box.

Deselect Standardized Residual as the y variable and select Cook's Distance as the y variable.

Deselect diam as the x variable and select Centered Leverage Value as the x variable.

Select type as the case labeling variable.

Click OK.

The resulting scatterplot shows a point far to the right of the others.

To identify the point, activate the graph by double-clicking on it.

Click the Point Identification tool.

Select the point. It is identified as a Tray.

This case has a high leverage and high influence. Its high leverage gives it extra weight in the computation of the regression line, and the high influence indicates that it did affect the slope of the regression line. You can deal with an influential point by using a weighting variable that gives the influential point less weight.