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ValueError: The mean chi2 statistic of trait 1 is less than 1.02, which is too small to be well-suited for MTAG.

Open cks2903 opened this issue 6 years ago • 7 comments

When running MTAG I get an error message saying that the mean chi2 statistic of trait 1 is less than 1.02. What exactly is this referring to, and how can I proceed from here? I've attached the .log-file. OWtraitsMTAG.log

cks2903 avatar Aug 17 '18 11:08 cks2903

Hi! Sorry for the slow turn-around on this.

We've recently updated the MTAG code so it throws an error when at least one trait has a mean chi2 statistic of less than 1.02. The reason for this is that in this range, we haven't carefully tested how robust MTAG is, and there are reasons to believe the results may become a bit unstable. For example, if the mean chi2 statistic is less than one, MTAG can't even produce valid standard errors in many cases.)

If you feel comfortable with your application (e.g., if you are confident that the traits that you are using are highly genetically correlated), then we have added an option to force MTAG to produce estimates. I think we called it --force. Please correct me if I'm wrong @huilisabrina.

paturley avatar Aug 20 '18 15:08 paturley

Thank you for your answer. I am confident about the correlation, so forcing the model would be okay. However, the MTAG code doesn't seem to recognize --force.

cks2903 avatar Aug 21 '18 11:08 cks2903

Hi @cks2903 ,

I was one step behind Patrick - I just added the --force option which functions as @paturley described. Could you try repulling the repo and run MTAG with --force?

Thanks, Hui

huilisabrina avatar Aug 22 '18 15:08 huilisabrina

Thank you, that solved my problem!

cks2903 avatar Aug 22 '18 17:08 cks2903

Wonderful. Glad it worked.

On Wed, Aug 22, 2018 at 1:04 PM cks2903 [email protected] wrote:

Thank you, that solved my problem!

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paturley avatar Aug 22 '18 17:08 paturley

I was wondering what is the mean chi2 statistic referring to?

cks2903 avatar Aug 23 '18 07:08 cks2903

The mean chi2 statistic is the mean value of the chi2 statistic (or the square of the z-statistic) across the SNPs in your data. It's equal to one (in expectation) if no SNP is associated with the trait and increases linearly in sample size otherwise. As such, it is a measure of the overall statistical power of the GWAS you are passing into the program.

On Thu, Aug 23, 2018 at 3:29 AM cks2903 [email protected] wrote:

I was wondering what is the mean chi2 statistic referring to?

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paturley avatar Aug 23 '18 12:08 paturley