I am estimating twin data using the standard model (https://openmx.ssri.psu.edu/docs/OpenMx/2.7.9/GeneticEpi_Path.html).
It appears that the program is having difficulty estimating the standard error (or confidence intervals). In one case I get a ! in the A column for estimates of one of the ACE components. From what I have read, I know that " An exclamation point in the 'A' column indicates that the gradient appears to be asymmetric and the standard error may not accurately reflect the variability of that parameter. As a precaution, it is recommended that you compare the SEs with likelihood-based or bootstrap confidence intervals."
In another case, when I print the confidence intervals for A/V, three exclamation marks (!!!) also are printed. I don't know what this means, but parallel modeling in STATA using acelong reveals a potential problem with estimation of this same CIs.
Any recommendations? Is there a way to avoid the problem by using a different specification? When the SEs are inconsistent with the CIs, is either one more reliable? Or are both suspect?
Thanks for the help. I am, obviously, a newbie.
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Problem 1:
name matrix row col Estimate Std.Error A
2 c ace 2 1 X.XX X.XX !
Problem 2:
confidence intervals:
lbound estimate ubound note
ACE.StdVarComp[1,1] X.XX X.XX X.XX !!!