Hi all.

I am conducting a mediation analysis (model 4) in SPSS using the PROCESS macro by Hayes. I have cross-sectional survey data and want to test the following relation:

Trait perfectionism (X) -> Emotion Dysregulation (M) -> Sound sensitivity (Y) I want to add one covariate in the analysis: a diagnosis of OCPD. My rationale behind this is that both OCPD and perfectionism are strongly related and therefore, as a covariate, such a diagnosis might have an effect on Y.

When adding it to the model, however, it has no statistical significance and the effect is negligible. Therefore, does it make sense to retain it as a covariate if ONLY 12 participants (out of 145) have reported a diagnosis of OCPD?