Hoping you can clarify for me on the appropriateness of method of outlier removal in GI testing.

It is part of the ISO standard that outliers outside 2 standard deviations can be removed to calculate GI.

However, some research centres stop after one round of outlier removals to get a final GI value while others recalculate the mean and standard deviation and do a 2nd (and 3rd and 4th if necessary) round of outlier removal until there are no more outliers.

I guess the question is, which is more appropriate?

Thanks for any input.