Using the Graphing page

Currently, the program will provide graphs for moderation analyses only. Three moderation analyses are supported. For the case with one moderator, a simple slopes and/or a confidence interval graph may be requested. For the other two cases, three of each graph will be produced.

Note that if a model contains interaction terms but no focal and moderator variables are selected on the Settings page, the Graphing page will not be available.

For more on these graphs, please use the links below:

Types of moderation

Case 1: One moderator

In Case 1, the predictor or moderator variable X2 moderates the relationship between the focal variable X1 and the outcome. This corresponds to the equation

For Case 1, one simple slopes and one confidence interval graph may be requested.

Case 2: Two independent moderators

Consider the case where the relationship between the outcome and a predictor (denoted as X3 in the image below) is moderated by two predictors (X1 and X2). While it is assumed that these two variables moderate the relationship, they are independent of each other.

This corresponds to the equation

For Case 2, three simple slopes and three confidence interval graphs will be produced.

Case 3: Two dependent moderators

In this case, there are again two predictors moderating the relationship between the outcome and a focal predictor (denoted as X3) in the image below. However, in contrast with Case 2, where two independent moderators are present, here the two moderators X1 and X2 are dependent.

This corresponds to the equation

For Case 2, three simple slopes and three confidence interval graphs will be produced.

Description of graphs

The first of the available graphs is a plot of the conditional regression line(s) describing the relationship between the outcome and the focal predictor as a function of the moderator. The plot will automatically show a line at each of three values of the moderator variable: mean – 1 standard deviation, mean, and mean + 1 standard deviation. In other words, the value of the moderator variable is held constant at three specific values. Values of the focal variable are used to define the x-axis, and the plot is confined to the area (mean of focal variable – 2 standard deviations, mean of focal variable + 2 standard deviations).

The plot is produced as a *.png file with the name <syntax file name>_simple_slopes.png which can easily be inserted into a paper. A number of plot settings may also be modified by the user on the Graphing page within the program.

The second plot shows the regression line describing the relationship between the outcome and the focal predictor as a function of the moderator, along with a 95% confidence interval. It also shows the so-called region of significance, provided that the boundaries of this region falls within the scale set by the values of the moderator variable, which again defines the x-axis. The region between the lower and upper bound of the region of significance indicates the values of the moderator for which the slope of the regression of outcome on focal variable transitions from non-significance to significance.

An example of the confidence interval plot with regions of significance is shown below. The plot produced by the program is saved to a *.png file with the name <syntax file name>_confidence_interval.png.

Changing graph parameters

Graphs can be modified using the Graphing page. This page is only available for moderation analyses. When this page is first opened, all options are set to default values. By default, both a simple slopes and a confidence interval graph will be produced.

All options are activated and may be changed. The image below shows a modified selection, requesting black and white graphs. For moderation model 1, there will only be one simple slopes graph and/or one confidence interval graph; for models 2 and 3 there will be three of each. In all cases, however, the following options apply: