st: power analysis for CFA

["Giuseppina Chiri" <gchiri@brandeis.edu>]

Dear stata list members,
I am writing to ask for help carrying out a power analysis for CFA using
STATA. I read in Timothy Brown's book "Confirmatory Factor Analysis for
Applied Research" that is possible to carry out power analysis using the
Satorra-Saris method. He gives an example using LISREL, SPSS and SAS. From
the provided covariance matrix, I was able to obtain a dataset of 500
observations and 6 variables and to successfully replicate his results. 

I first create the dataset

clear 
matrix input m = (1, .4550, .4680, .1365, .1592, .1479 \ .455, 1, .504,
.147, .1715, .1592 \ .468, .504, 1, .1512, .1764, .1638 \ .1365, .147,
.1512, 1, .4200, .3900 \ .1592, .1715, .1764, .4200, 1, .4550 \ .1479,
.1592, .1638, .3900, .4550, 1)
matrix list m

set seed 12345
set obs 500
corr2data x1 x2 x3 x4 x5 x6, cov(m)

list in 1/10, sep(0)
corr x1-x6

Then I run SEM based on the model in the book

sem (L1 -> x1, ) (L1 -> x2, ) (L1 -> x3, ) (L2 -> x4, ) (L2 -> x5, ) (L2 ->
x6, ), covstruct(_lexogenous, diagonal) standardized latent(L1 L2 ) cov(
L1*L2) nocapslatent standardized

My results match those in the book.   

Brown also provides the SPSS and SAS to carry out the power analysis, which
I translated into STATA as: 

gen power = 1 - nchi2(df,ncp,chicrit)
list n ncp power, noobs clean table

Using the df ncp and chicrit values provided in the book, I was able to
obtain the power estimate.

What I am having difficulties with is figuring out where the two values
chicrit = 3.841459 and ncp = 6.3724 are coming from. Looking at the STATA
output I don't see these numbers, not even after asking for gof stats.
What am I missing? 
Any suggestions would be greatly appreciated.
Giusi








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