[R] Tetrachoric correlation in R vs. stata

Janet Rosenbaum jrosenba at rand.org
Fri Jun 23 19:42:12 CEST 2006

I hope someone here knows the answer to this since it will save me from 
delving deep into documentation.

Based on 22 pairs of vectors, I have noticed that tetrachoric 
correlation coefficients in stata are almost uniformly higher than those 
in R, sometimes dramatically so (TCC=.61 in stata, .51 in R;  .51 in 
stata, .39 in R).  Stata's estimate is higher than R's in 20 out of 22 
computations, although the estimates always fall within the 95% CI for 
the TCC calculated by R.

Do stata and R calculate TCC in dramatically different ways?  Is the 
handling of missing data perhaps different?  Any thoughts?

Btw, I am sending this question only to the R-help list.




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