Finding the Best Fitting Line

The following applet, named FindLine, allows you to move the regression line vertically (i.e. changing its intercept) and to rotate it (i.e. changing its slope). The data in the applet are taken from McClelland’s original applet, and show the scores on a Statistical Knowledge Quiz (SKQ) before and after students have taken his statistics course.

Drag the blue square to move the line up and down. Drag anywhere else on the line to change the slope. Clicking anywhere in the graph causes the line to jump so that it goes through the point clicked.

Adjust the line until you think that it is a “best fit.” I happen to know that the best fitting line has an intercept of 10.9, and a slope of 0.42. How does the line you fit compare to that?
In the next applet I have entered the data on alcohol and tobacco use from Table 9.3 in Chapter 9. Find the best fitting line by eye, and compare that to the values that we computed in Table 10.5, with and without Northern Ireland.

Comments to: Gary.McClelland@Colorado.edu

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