If I have two categorical IVs and one continuous IV and I want to see if the two categorical IVs predict a continuous DV over and above the effect of the continuous IV, what analysis should I use?
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1 Answer
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You can use partial regression plots.
If the plot of residuals of the following regressions show a pattern, then yes, the categorical IVs are indeed adding further value.
- Regress Y on the categorical IVs
- Regress the categorical IVs against the continuous IVs
Use the residual plots of 1 vs 2 to see if the categorical IVs are adding any additional value.
