step  To produce a scatterplot of time by diam, from the menus choose:

Graphs
 Scatter...

step  Click Define.

step  Select time as the y variable and diam as the x variable.

step  Click OK.

These selections produce the scatterplot.

step  To see a best-fit line overlaid on the points in the scatterplot, activate the graph by double-clicking on it.

step  From the Chart Editor menus choose:

Chart
 Options...

step  Select Total in the Fit Line group.

step  Click OK.

The resulting scatterplot appears to be suitable for linear regression, with two possible causes for concern.

  • The variability of polishing time appears to increase with increasing diameter.
  • The point on the far right of the graph may exert an undue amount of influence on the lay of the regression line.

You will investigate these concerns further during diagnostic checking of the regression model.