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Running EFA using Polychoric correlations

• 1.  Running EFA using Polychoric correlations

Posted Mon May 29, 2023 09:49 AM

Hello,

I would like to run a EFA on my questionnaire to determine construct validity, however, my data is dichotomous.

I have checked the literature and it has been suggested to run a polychoric correlation matrix instead and then use factor analysis on the matrix generated.

I have generated a polychoric matrix using the following steps: ANALYSE -> CORRELATIONS -> HETEROGENEOUS CORRELATIONS

My question is how to run a EFA using the polychoric matrix that I have generated?

When I try to run the factor analysis SPSS uses the Pearson's correlation matrix (ANALYSE -> DIMENSION REDUCTION -> FACTOR). How would I select my Polychoric matrix to run the factor analysis instead of Pearson's?

I am quite new to SPSS, any help would be appreciated.

Thank you.

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Sonya Rafiq
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• 2.  RE: Running EFA using Polychoric correlations

IBM Champion
Posted Mon May 29, 2023 07:38 PM
In order to use the polychoric matrix from HETCOR, you need to capture it using OMS (table subtype is 'HeterogeneousCorrelations').  Then you need to turn it into MATRIX DATA - see the Command Syntax Reference.  That can then be used as input to FACTOR via the MATRIX subcommand.
I have attached an example  using the employee data.sav file shipped with SPSS Statistics.

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Jon Peck
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Attachment(s)

hetcorExample.txt   1 KB 1 version

• 3.  RE: Running EFA using Polychoric correlations

Posted Tue May 30, 2023 09:45 AM

Please note that tetrachoric or polychoric correlation matrix is not always positive definite (p.d). FACTOR procedure, IIRC, will need a p.d. matrix for input.

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Kirill Orlov
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• 4.  RE: Running EFA using Polychoric correlations

Posted Tue May 30, 2023 09:46 AM

Please look in Command Syntax Reference, FACTOR command, for how to input a correltion matrix fo factor analysis. You will be able to do extraction and rotation oc the factors, but not computation of factor scores (because you "don't have" data to input.

You might want also to check this answer and further links therein https://stats.stackexchange.com/questions/215404/is-there-factor-analysis-or-pca-for-ordinal-or-binary-data/215483#215483
And your tetrachoric or polychoric correlation matrix should happen to be positive definite ("gramian") in order to submit it to FACTOR successfully.

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Kirill Orlov
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