[R] Simulating dataset using Parallel Latent CTT model?

[William Revelle]

Nidhi,



Presumably, you are trying to simulate 20 items all sharing one 
general factor but having some error.

The model as you specified it has no error.  Thus all the 
correlations will be 1 and the factors will not make any sense.

Most items have loadings on a general factor of  the  order of about 
.4 to .6.  You might try:

GenData <- congeneric.sim(N=500, loads = rep(.5,20), short = FALSE)
Then you will find that the factor scores  found by factor.pa 
correlate at .93 with the latent variable.

>  FactorScore=factor.pa(GenData$observed,1,scores = "TRUE", rotate="none")
>  round(cor(FactorScore$scores,GenData$latent),2)

Bill




At 8:27 AM -0500 12/26/08, Nidhi Kohli wrote:
>I am trying to simulate a dataset using Parallel Latent CTT model 
>and this is what i have done so far:
>
>(START)
>
>#Importing psych library for all the simulation related functions
>
>library(psych)
>
># Settting the working directory path to C:/NCME
>
>path="C:/NCME"
>setwd(path)
>
>#Using the function to generate the data
>
>GenData <- congeneric.sim(N=500, loads = 
>c(1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1), short = FALSE)
>
>#Rounding upto 2 decimal places while showing the correlation matrix
>
>round(cor(GenData$observed),2)
>
>#Factor Score
>FactorScore=factor.pa(GenData$observed,1,scores = "TRUE", rotate="none")
>round(cor(FactorScore$scores,GenData$latent),2)
>
>(END)
>
>Please let me know if I am moving into the right direction, if not 
>then, please let me know the correct way to simulate the dataset
>
>Thanks in Advance
>
>Regards,
>
>Nidhi Kohli
>***************************************
>Nidhi Kohli, M.Ed.
>Doctoral Student
>Department of Measurement, Statistics
>  and Evaluation
>University of Maryland
>1230 Benjamin Building
>College Park, MD 20742-1115
>
>e-mail: nidhik at umd.edu
>
>______________________________________________
>R-help at r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.


-- 
William Revelle		http://personality-project.org/revelle.html
Professor			http://personality-project.org/personality.html
Department of Psychology             http://www.wcas.northwestern.edu/psych/
Northwestern University	http://www.northwestern.edu/
Attend  ISSID/ARP:2009               http://issid.org/issid.2009/