Interaction between two continuous variables

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*#:and ''b<sub>3</sub>'' indicates how much the slope of X<sub>1</sub> changes as X<sub>2</sub> goes up or down one unit.
*#:and ''b<sub>3</sub>'' indicates how much the slope of X<sub>1</sub> changes as X<sub>2</sub> goes up or down one unit.
*#It is then possible to factor out X<sub>2</sub>
*#It is then possible to factor out X<sub>2</sub>
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*#:Y<sub>''i''</sub> = (''b''<sub>0</sub> + ''b''<sub>1</sub>X<sub>1''i''</sub>) + (''b''<sub>2</sub>+ ''b''<sub>3</sub>X<sub>1''i''</sub>) X<sub>2''i''</sub> + ''e<sub>i</sub>''
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<sub>
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*#:where (''b''<sub>2</sub>+ ''b''<sub>3</sub>X<sub>1''i''</sub>) represents the effect of X<sub>2</sub> on Y at specific levels of X<sub>1</sub>
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*#:and ''b<sub>3</sub>'' indicates how much the slope of X<sub>2</sub> changes as X<sub>2</sub> goes up or down one unit.

Revision as of 05:45, 30 October 2006

Statistical programs, like SPSS, do not always have "point-and-click" commands for every possible statistical test. This page is a description of how to test the interaction between two continuous variables. Below, an explanation of interactions is presented, then the three steps to conduct the interaction is described, and examples are given to help in understanding the steps involved.

What is an interaction?


Three Steps

Plotting the interaction

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