SPSS moderation and mediation PDF

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SPSS INSTRUCTIONS FOR MODERATED REGRESSION Centering      

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     

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       

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   

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

 

  

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



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”



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



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    

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)...