[R-sig-ME] contextual effects in 3-level models
Timothy MacKenzie
|@w|@wt @end|ng |rom gm@||@com
Mon Sep 6 20:31:12 CEST 2021
Dear All,
Suppose X is a continuous predictor that can vary within and between
two nested grouping variables in a 3-level linear mixed model:
effect.size ~ X + (1 | studies/outcomes)
How can I obtain the within effect of X, contextual effect of X at
level 2, and contextual effect of X at level 3?
I can think of two options but wonder which one makes more sense
(below)? For both options, I will fit:
effect.size ~ X + X_ave_study + X_ave_outcome + (1 | studies/outcomes)
Thank you,
Tim
library(dplyr)
#-- Option 1:
data %>%
group_by(study) %>%
mutate(X_ave_study = mean(X)) %>%
group_by(outcome) %>% ## Here mean of
outcome *ignoring* studies is computed
mutate(X_ave_outcome = mean(X))
#-- Option 2:
data %>%
group_by(study) %>%
mutate(X_ave_study = mean(X)) %>%
group_by(outcome, .add = TRUE) %>% ## Here mean of outcome
*within* each study is computed
mutate(X_ave_outcome = mean(X))
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