[R-sig-ME] Question about interpreting interaction of effects coded predictors

[David Sidhu]

Hi There

I have run a mixed effects logistic regression with two dichotomous predictors and their interaction. These predictors were effects coded (i.e., -1, 1).
Can I simply interpret the term for the interaction that is provided by a model summary? Or, is there another step that is necessary for testing the interaction that includes an ANOVA function? (A reviewer suggested the latter.)

I have attached some code for running an analysis of the sort I’m talking about.

Thanks very much!
Dave



require(lme4) require(lmerTest) require(data.table) Subject <- rep(1:30, each = 12) Item <- rep(1:12, times = 30) IV1 <- rep(rep(c("A", "B"), each = 6), times = 10) IV2 <- rep(c("A", "B"),times = 180) DV <- sample(c(0,1), replace = TRUE, size = 360) data <- as.data.table(cbind(Subject, Item, IV1, IV2, DV)) data$IV1 <- as.factor(data$IV1) data$IV2 <- as.factor(data$IV2) data$DV <- as.factor(data$DV) contrasts(data$IV1) <- c(1, -1) contrasts(data$IV2) <- c(1, -1) m <- glmer(DV ~ IV1*IV2 + (1|Subject) + (1|Item), family = "binomial", data = data) summary(m)

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David M. Sidhu<http://davidmsidhu.com>, PhD
Postdoctoral Associate
Department of Psychology
University of Calgary







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