Hi all

By Using Minitab, when GR&R study is conducted (crossed method), what are the conditions when % of contribution or % of study variation is a more appropriate metric to use?
Thanks in advance

% of study variation is %GRR. This is the appropriate metric to use to determine whether a gage is suitable for use in process control, or in continual improvement (hypothesis test, DOE's, etc.).

% contribution is a tool, not a metric. Its only purpose is to point you to the parameter (i.e., repeatability, reproducibility, operator x part interaction, etc.) that contributes the most to the measurement variation. That allows you to focus on the correct parameter to reduce measurement variation.

In that case why Minitab displays a Total GR&R % in % Contribution?
It seems just to be the addition of EV and AV.. not the square root of (EVsqure + AVsquare). am I right?

Minitab bases the % Contibution on the variances (VarComp), which are additive. The variance (VarComp) of the repeatability is EVsquared. The variance of the reproducibility is AVsquared.