This book, the first in a series dedicated to Standardized Work, is about operator performance measurement. Describing how to measure the performance of operators quickly and simply, it explains how to identify the most efficient operators and how to monitor their improvement over time. The method described can be automated very easily, thereby requiring no labor consumption. The approach is grounded in one of the basic laws of factory physics: mastery of variability. The method presented here has been applied with success for years in automotive industry.