Published on *OpenMx* (http://openmx.psyc.virginia.edu)

By *dwils03*

Created *02/09/2013 - 11:46*

Sat, 02/09/2013 - 11:46 — dwils03 [1]

Hello Helpful Forum Members,

My co-authors and I have been very happy with the metaSEM R package, and we're grateful to the authors and contributors for their hard work in developing and maintaining the package.

I've been stuck for a while at a crucial part of "stage 2" of the TSSEM approach, and I'm hoping that someone here can help me make sense of it. Specifically, I'm confused about the syntax used to specify the structural model to be fit to the pooled data derived in stage 1.

I'll reference the documentation file ("metaSEM: An R Package for Meta-Analysis using Structural Equation Modeling"), which is available here: http://courses.nus.edu.sg/course/psycwlm/internet/metaSEM/metasem.pdf [2].

On page 26 of that file, an example of how to specify the structural model is given:

(And I hope the table structure displays properly.)

EDIT: It didn't; sorry.

R> A1

A C ES E I Alpha Beta

A "0" "0" "0" "0" "0" ".3*Alpha_A" "0"

C "0" "0" "0" "0" "0" ".3*Alpha_C" "0"

ES "0" "0" "0" "0" "0" ".3*Alpha_ES" "0"

E "0" "0" "0" "0" "0" "0" ".3*Beta_E"

I "0" "0" "0" "0" "0" "0" ".3*Beta_I"

Alpha "0" "0" "0" "0" "0" "0" "0"

Beta "0" "0" "0" "0" "0" "0" "0"

My question is about the values given for each of the loadings on the two factors (Alpha and Beta). It appears that each path is given a name ("Alpha_A"), but that it is multiplied by a decimal value. It may not be multiplication, of course, but instead something specific to the syntax. What do the numbers and asterisks mean prior to the name of the path? Is this some sort of scaling specific to the sample problem? The S matrix contains similar values in each of the parameter spots. I've just never seen this syntax before and I'm confused.

Perhaps this syntax is borrowed from a different package that used by the metaSEM package? If so, maybe someone could refer me to that package's documentation, which might more clearly explain the syntax for model specification. The explanations provided in the metaSEM documentation are sparse on this point.

I look forward to reading your responses. Thank you!

**Links:**

[1] http://openmx.psyc.virginia.edu/users/dwils03

[2] http://courses.nus.edu.sg/course/psycwlm/internet/metaSEM/metasem.pdf

[3] http://openmx.psyc.virginia.edu/thread/1986

[4] http://openmx.psyc.virginia.edu/thread/1724

[5] http://openmx.psyc.virginia.edu/forums/third-party-software/metasem