SPSS INSTRUCTIONS FOR MODERATED REGRESSION
Centering
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Find the mean of the variable you want to center (you already know how to do this in
SPSS)
Go to “Transform” then “Compute”
In the box that says “target variable” rename the variable you want to center (if your
original variable is “ragree” then “cragree” would be a good new variable name)
Double click the variable that you want to rename (this should make it go into the
“numeric expression” box).
Subtract the mean from this variable, so if the mean for ragree is 50 you would have an
expression that looks like this: ragree-50
Click “ok”, you should see a new variable “cragree” in your dataset
Creating interaction terms
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Go to “Transform” then “Compute”
In the box that says “target variable” create a name for your interaction term (usually
something beginning with an “i” helps denote an interaction term).
Place the variables that you want to create an interaction term from in the box that says
“numeric expression.” You must multiply your variables together.
For example, if you want to create an interaction between “ragree” and “recip” your
expression will look like this: ragree*recip
Click “ok”, and you should see a new variable term representing your interaction.
Running a Moderated Regression
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Go to “Analyze” then “Regression” then “linear”
Place your DV in the box that says “dependent”
In step 1 of your regression, place your main effects (your independent variables that
made up your interaction) in the box that says “independent(s). For example, you would
place “ragree” and “recip” in step 1.
Click “Next”
In step 2 of your regression place your interaction term.
Click “Statistics” and check off rsquare change, descriptives, confidence intervals,
collinearity diagnostics, and part and partial correlations.
Click “ok” to get out of this menu, and then “ok” again in the main menu.
Creating a Plot in Excel
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To create a plot, use the excel spreadsheet posted online.
At the bottom of excel you will see the option to go to either a spreadsheet labeled
“formula”. Go to “formula”
Place your regression coefficients in column B:
(Constant)
Exam Performance
General Self-Efficacy
ExamXGen
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b
63.19
0.28
8.15
-0.30
Your intercept value will go in the row designated “constant”
Your unstandardized coefficient for your IV will go in the box next to the row
designated “Exam performance” this represented the IV in the class example. It
will help if you rename this row to represent the IV you are using in the
homework.
Your unstandardized coefficient for the variable representing your moderator will
go in the box next to the row designated “General Self-Efficacy”. Again, it will
help if you rename this row to represent the Moderator you’re using.
Finally, the unstandardized coefficient representing your interaction term will go
in the box next to the row labeled “Exam*Gen”. Again, rename this.
Below these rows you will see this:
Exam Performance
General Self-Efficacy
-1SD
-19.02
-0.50
0SD
0.00
0.00
+1SD
19.02
0.50
Again, Exam Performance represents the IV and General Self-Efficacy the
Moderator.
 In the column that says 0SD, place the means of each of your variables in their
respective boxes.
 Determine what +1sd above and -1sd below each of these variables/means
would be and then place those variables in the appropriate boxes.
Excel will derive values representing each combination of +1sd and –1sd for these two
variables. You will see these values in the rows below:
-1SD Exam, -1SD Gen
0SD Exam, -1SD Gen
+1SD Exam, -1SD Gen
-1SD Exam, 0SD Gen
0SD Exam, 0SD Gen
+1SD Exam, 0SD Gen
-1SD Exam, +1SD Gen
0SD Exam,+1SD Gen
+1SD Exam, +1SD Gen
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50.88134
59.117
67.35266
57.80734
63.19
68.57266
64.73334
67.263
69.79266
Now, you have all of the info you need to create your plot. Click on the box at
the bottom of “excel” designated “Interaction Plot”
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IV
Low
Medium
High
Place the values that “excel” generated for you in the appropriate boxes. So
for example, the value that represented –1 Sd for the IV and –1sd for the
moderator was 50.88. We see in table below, that the cell corresponding both
low IV values and low Moderator values has a value of 50.88.
Moderator
Low
Medium
High
50.88134 57.80734 64.73334
59.117
63.19
67.263
67.35266 68.57266 69.79266
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Once you’ve placed the correct values into those cells, follow the
directions listed at the bottom of the excel spreadsheet.
SPSS INSTRUCTIONS FOR MEDIATED REGRESSION
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To test for mediation, you basically run 3 separate regressions (2 simple
regressions and 1 multiple regression.
For your first regression, regress the mediator onto the IV.
For your second regression, regress the DV onto the IV.
For your third regression, regress your DV onto both the IV and
Moderator.
(YOU SHOULD ALREADY KNOW HOW TO RUN A SIMPLE AND
MULTIPLE REGRESSION IN SPSS)