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Building upon How to simulate type I error and type II error, I would like to simulate type I error for a random-effects model I generated.

The statistic of interest is standard deviations of the random intercept and random slope. Specifically, for random intercept, H_{0}: lambda_{0} =2 and H_{1}: lambda_{0} not equal to 2; for random slope, H_{0}: lambda_{1} =1 and H_{1}: lambda_{1} not equal to 1. I assume the test would be likelihood ratio test but please correct me if I am wrong. How do I assess type I error for the random-effects model I specified below:

set.seed(323)
#The following code is to specify the structure and parameters of the random-effects model
dtfunc = function(nsub){
  time = 0:9
  rt = c() 
  time.all = rep(time, nsub)
  subid.all = as.factor(rep(1:nsub, each = length(time)))
  
  # Step 1:  Specify the lambdas.  
  G = matrix(c(2^2, 0, 0, 1^2), nrow = 2)  
  int.mean = 251  
  slope.mean = 10  
  sub.ints.slopes = mvrnorm(nsub, c(int.mean, slope.mean), G)
  sub.ints = sub.ints.slopes[,1]
  time.slopes = sub.ints.slopes[,2]
  
  # Step 2:  Use the intercepts and slopes to generate RT data
  sigma = 30      
  for (i in 1:nsub){
    rt.vec = sub.ints[i] + time.slopes[i]*time + rnorm(length(time), sd = sigma)
    rt = c(rt, rt.vec)
  }
  
  dat = data.frame(rt, time.all, subid.all)
  return(dat)
}

#Here I run one random-effects model
set.seed(10) 
dat = dtfunc(16)
lmer(rt~time.all + (1+time.all |subid.all), dat)

Assuming the test for significance is likelihood ratio test and so in the end, I want to see if I run the test 1000 times, what is the probability of rejecting null hypothesis when it is TRUE. Also, how do I plot the behavior of type I error if I change the values of standard deviations?

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