RM-ANCOVA

#1
Hi, I am running RM-ANCOVA in SPSS, where I have an immune marker measured at 2 different time points - this is my within-subject factor.

For my between-subject factor, I have Vit D dosage. I want to look at the interaction between the immune marker at the 2 different time points and Vit D dosage (immune marker*Vit D dosage).

However, when I add age and sex as covariates, the output gives interaction terms for immune marker*age and immune marker*sex.

I have a small sample size, so I don't want this many interaction terms. Is there any way to select which interaction terms you want to run in SPSS (e.g. if I only want interaction with the main effect and not all covariates)?
 
Last edited:

Karabiner

TS Contributor
#2
In the SPSS window for the RM ANOVA there is a button "model" which leads to the window where you can construct
a custom (RM-)ANOVA.

With kind regards

Karabiner
 
#3
In the SPSS window for the RM ANOVA there is a button "model" which leads to the window where you can construct
a custom (RM-)ANOVA.

With kind regards

Karabiner
The custom option when you press the "model" button doesn't allow you to limit the interactions between each immune marker and the covariates. It just gives you an option to build extra interaction terms between the between-subject factors and the covariates. I don't want added interaction terms...I want to know if there is a way to limit the interaction to the main effect only.
 

Karabiner

TS Contributor
#4
In the lower part of the window, you can specify a) which between-subject predictors (factprs, covariates)
you want to include, and b) which interactions you want to include.

With kind regards

Karabiner