[R-meta] Score Normalization for Moderator Analysis in Meta-Analysis

[Kiet Huynh]

Hello colleagues,

I’m conducting a meta-analysis of the association between LGBTQ+ discrimination and mental health. Both are continuous variables, and I am analyzing correlation coefficients. I’m interested in looking at moderators (continuous) of the relationship between these two variables. One such moderator is social support (continuous). I am considering two approaches for running the moderator analysis:

1) Many of the studies used the same MSPSS social support scale. I plan to use the mean value of the MSPSS as a continuous moderator variable of the discrimination-mental health relationship.

2) Most studies, however, use different measures of social support. I plan to use the min-max normalization method to put all the social support measure on the same scale, and then use that normalized mean as the moderator variable of the discrimination-mental health relationship. For an example use of min-max normalization method, see Endendijk et al. (2020). However, the Endendijk et al. (2020) study uses the min-max normalization method for the outcome and not for a moderator. The formula for the min-max normalization method is:

x’ = (x - min)/(max - min)
x’ is the normalized mean, x is the mean of the sample, min is the minimum possible value of the scale, and max is the maximum possible value of the scale.

The benefit to the second approach is that I can include more studies in this moderator analysis, and not just the studies using the same measure of social support. 

My question is whether both approaches are valid methods for testing moderator analysis? Are there any issues with using the of min-max normalization method for moderator analysis?

Thank you,

- KH

Reference:

Endendijk, J. J., van Baar, A. L., & Deković, M. (2020). He is a stud, she is a slut! A meta-analysis on the continued existence of sexual double standards. Personality and Social Psychology Review, 24(2), 163–190. https://doi.org/10.1177/1088868319891310

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Kiet Huynh, PhD (he/him) 
(hear pronunciation <https://www.name-coach.com/kiet-huynh-94be0772-1bfd-4ece-afba-14699186f2b9>)
Assistant Professor
Department of Psychology

Terrill Hall Rm # 336
University of North Texas
Denton, TX 76203
Kiet.Huynh using unt.edu <mailto:Kiet.Huynh using unt.edu>
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