IntGraph.xlt, Version 1.0

                   Brettfeld & Enzmann, 2003

The Excel template IntGraph can be used to plot the lines of a
regression equation with an interaction term. The three lines
represent the lines of the regression of a dependent variable Y
on an independent variable X corresponding to the mean of the
moderator variable Z, one standard deviation above Z, and one
standard deviation below Z, respectively.

With IntGraph the role of the moderator variable can easily be
changed from Z to X. In this case the three lines represent the lines
of the regression of the dependent variable Y on Z corresponding to
the mean of the moderator variable X, one standard deviation above X,
and one standard deviation below X, resp.

The user has to enter the means and standard deviations of X and Z,
and the values of b0 (the constant), b1 (the unstandardized
regression coefficient of X), b2 (the unstandardized regression
coefficient of Z), and b3 (the unstandardized regression coefficient
of the interaction term or the product X*Z). If the regression
equation is based on centered data, the means of X and Z are zero. If
the variances of X and Z are entered, buttons can be used to
transform them into their respective standard deviations (this action
can be reversed). In the table sheet, only values displayed in blue
should be changed.

The user can specify variable names and significance levels of the
regression parameters. The display of the effects on the graph is
optional. Additionally, the user can modify (or delete) all elements
of the graph, including the legend of the regression lines. However,
the Excel template itself should not be modified, Excel automatically
saves the produced graph including its table sheet as a different
XLS-file.

The default values of the template IntGraph correspond to the first
example in Aiken & West (1991). The book contains a detailed
discussion of continuous variable interactions. Another classical
source is Cohen & Cohen (1983) or its revised and enlarged edition
(Cohen et al., 2003).

The Excel template is available at
http://www2.jura.uni-hamburg.de/instkrim/kriminologie/Mitarbeiter/Enzmann/Software/Enzmann_Software.html

Comments for further improvements are welcome.

References

Aiken, L.S. & West, S.G. (1991). Multiple regression: Testing  and
   interpreting interactions. Newbury Park, CA: SAGE.
Cohen, J. & Cohen, P. (1983). Applied multiple regression / correlation
   analysis for the behavioral sciences. Hillsdale, NJ (2nd ed.):
   Erlbaum.
Cohen, J., Cohen, P., West, S.G. & Aiken, L.S. (2003). Applied multiple
   regression / correlation analysis for the behavioral sciences.
   Mahwah, NJ (3rd ed.): Erlbaum.