MSA 4th Edition Changes

Variable Gage R&R The report form on page 119 is identical to the MSA 3rd edition form (pg 114) All constants remained the same. All formulas remained same for Part to Part Variation method. For Tolerance method, the Part Variation (PV) changed from PV = Rp x K3 to PV = sqrt((TV)(TV)-(GRR)(GRR)). Number of Distinct Categories (ndc) remained the same.

Attribute Gage R&R Crosstab method form and formulas remained unchanged. Analytical method is equivalent between 3rd and 4th edition. Tstatistic formula changed from t = (31.3 x Bias)/R to t = (6.078 x Bias)/σrepeatability. Since, σrepeatability = R/5.15 and 5.15 x 6.078 = 31.3, the formulas are equivalent. No changes are required for Attribute forms.

Bias, Linearity, Stability For Bias & Linearity, the 4th edition now specifies that the repeatability acceptability must first be determined using %EV = 100[EV/TV] = 100[σrepeatability/TV]. The specification range / 6 can be substituted for TV. The formulas for calculating the bias acceptance have been changed with the d2 and d2* constants removed. Formulas for calculating Linearity remain unchanged. The section on Stability has not changed.

Destructive Testing No changes or additions on how to handle destructive tests.