Do we need normal data for gage r&r studies?

Hello guys,

Is the measurement data should be normal when we do gage r&r studies? Is the normality of data play any important role in gage studies?

Thank you

The quick answer is NO.

Technically, the residuals of the ANOVA analysis should be normally distributed. However, with a typical sample size of 90 (3 x 3 x 10), the normality assumption is no longer important. Regardless, normality of the raw data is never a requirement.

Thank you for the quick answer miner...
When we have to check for normality in general?

For a standard MSA, you should never have to check for normality. Normality becomes important when you perform capability studies or certain statistical analyses that depend upon the assumption of normality.

Adding to Miner's excellent comments remember that SPC doesn't require Normality either....and capability studies only require normality when you are conflating the index with a projected defect rate that relies on the Normal distribution model. Normality is a special unique occurrence. is not typical or necessary.

@Bev D Notice I did not mention SPC.