good question. I don't think there is anything wrong with multiplying two zs, but it might be more appropriate to multiply the raw covariates and then compute a z from that.
On 11/30/2020 4:07 AM, Marina Fernández wrote:
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Dear all,
I am doing a multiple regression analysis with 3 covariates of interest. I know that for testing two-way and three-way interactions I must create new variables by multiplying the covariates of interest. As Freesurfer transforms continuous variables to z score before applying statistic, is it correct to transform to z score the result of the previous multiplication? I am asking this because the result of multiplying two z transformed variables would be different.
Thanks a lot in advance.
Marina
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