Modification Indices and Sample Size PreviousNext
Mplus Discussion > Confirmatory Factor Analysis >
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 Lucy Gallienne posted on Thursday, November 25, 2010 - 1:34 am
Hi,
I was wondering if the modification indices are sensitive to large sample sizes? For instance if I have a larger sample size, will more modification indices come up as significant?
Thanks for your help,
Lucy
 Linda K. Muthen posted on Thursday, November 25, 2010 - 2:50 pm
Yes.
 Lucy Gallienne posted on Thursday, November 25, 2010 - 7:52 pm
Thankyou. Because of the large data set I have to work with, I am planning on taking a few random samples and doing the Mulitgroup Factor Analysis on these. I understand that large sample sizes also affect the ch-squared difference test. What sample sizes would you suggest would work best for the chi-square difference testing and MIs?
Thanks again,
Lucy
 Bengt O. Muthen posted on Friday, November 26, 2010 - 2:16 pm
Tough question since it depends on so many factors such as outcome distribution and model parameter values. Often with continuous-normal outcomes n=500 seems to be a middle of the road sample size.
 Lucy Gallienne posted on Tuesday, November 30, 2010 - 1:40 am
Thanks. To be more specific, I have ten items, each with 5 levels of response. At the moment I'm taking sample sizes of about 1000.
 Linda K. Muthen posted on Tuesday, November 30, 2010 - 2:38 pm
There are many factors that influence the sample size needed. See the following paper which is available on the website:

Muthén, L.K. & Muthén, B.O. (2002). How to use a Monte Carlo study to decide on sample size and determine power. Structural Equation Modeling, 4, 599-620.
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