What is the difference between “% contribution” and “% study” in terms of GRR performance?
% Contribution is determined by multiplying by 100 the proportion of the GRR variance to the total study variance. % Study is determined by multiplying by 100 the proportion of the GRR standard deviation to the total study standard deviation. Thus, a level of 20% study is equivalent to a level of 4% contribution (.2 x .2 = .04).
