Instructions

A "Begin" button will appear on the left when the applet is finished loading. This may take a minute or two depending on the speed of your internet connection and computer. Please be patient. If no begin button appears, it is probably because your browser does not support Java 1.1.

Starting the Applet and setting the conditions

Press the "Begin" button to start the applet in another window.

The simulation shows a scatterplot of data from a bivariate distribution in which the relationship between the two variables is linear. You can change the "input" values of slope, standard error of the estimate, or standard deviation of X for this data sample, and see the effects of your change.

On the right side, a blue and red bar shows the total variance in Y for the sample. The blue portion shows the amount of variance explained by X; the red portion shows the amount of variance unexplained.

The simulation also shows two "output" values, Pearson's r and the standard deviation of Y. These vary as a function of the three input values you can set.

You can change any of the input values and observe the effect on the scatterplot and the output values. Or, you can use the "animate" feature to watch what happens as the values change. If you click any of the "animate" buttons, the relevant parameter will change in small steps updating the scatterplot and the output values. This may not work with all browsers.

The same data sample is used for each change your make. To see new random data that correspond to your input values, click the "new data" button.

Credits

The simulations were developed as part of a grant from NSF to David Lane of Rice University. Partial support for this work was provided by the National Science Foundation's Division of Undergraduate Education through grant DUE 9751307. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.