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Assessing whether sigma for a random effects parameter is equal to 0

Sammie Haskin 
Hello! Given the pistonrings data set from the qcc package in R, I produced the following code to assess whether the standard deviation of random effect of the model was equal to 0. Here is my code:

library(lme4)
library(qcc)
library(RLRsim)
library(nlme)
library(data.table)

fit.pistons <- lmer(formula=diameter ~  sample + (1 | sample), data = pistonrings,REML=T)
fit.pistons0 <- lm(diameter ~ sample, data = pistonrings)
exactLRT(fit.pistons,fit.pistons0)

Here is the output:

LRT = 8.1423, p-value = 0.0014

Is this result implying that the standard deviation for the random effect is significant such that we reject the null hypothesis and that H0: sigma = 0 is false?

Thread (3 messages)

Sammie Haskin Assessing whether sigma for a random effects parameter is equal to 0 Oct 13 Ben Bolker Assessing whether sigma for a random effects parameter is equal to 0 Oct 13 David Duffy Assessing whether sigma for a random effects parameter is equal to 0 Oct 14