Fitting an outcome model that is within subject (model.y, using lmer) and a simple model for the mediator (`model.m`, using lm)? about mediation HOT 1 CLOSED

I found that there is an example in the mediate pagacke:

library(lme4)
library(mediation)

data("school", package = "mediation")
data("student", package = "mediation")

med.fit <- lm(smorale ~ free , data = school)
out.fit <- lmer(late ~ free + smorale + (1 | SCH_ID), data = student)

med.out <- mediate(med.fit, out.fit, treat = "free", mediator = "smorale", control.value = 3, treat.value = 4, sims = 100)
summary(med.out)

I just made sure that my data looked as similar as possible to the example. It is difficult to say what change did the trick, but here are a few things that I noticed:

• my group was not properly converted to an integer. I made sure that the values were 0 for the control and 1 for the intervention group
• I was using the subset parameter of lm. In the example, I used unique() to make it clear, but subset parameter definitely does not work

from mediation.