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| This [attachment:birril.pdf paper] suggests a way of using residuals to represent interaction terms to enable a stepwise (forward or backward) comparison of the interactions be performed in SPSS. This overcomes the problem of having to have the main effects, A and B, in a model, at all times, in a model with higher order interactions containing either, or both of, variables A and B. | This [attachment:birril.pdf paper] suggests a way of using residuals to represent interaction terms to enable a stepwise (forward or backward) comparison of the interactions can be performed in SPSS. This overcomes the problem of having to have the main effects, A and B, in a model, at all times, in a model with higher order interactions containing either, or both of, variables A and B. |
Using single variables to represent interactions
This [attachment:birril.pdf paper] suggests a way of using residuals to represent interaction terms to enable a stepwise (forward or backward) comparison of the interactions can be performed in SPSS. This overcomes the problem of having to have the main effects, A and B, in a model, at all times, in a model with higher order interactions containing either, or both of, variables A and B.
Reference
Burrill, D. (1998). Modelling and interpreting interactions in multiple regression. [On-line]. Also available at: http://www.minitab.com/burril2.htm.