Human Sigma is a branch of Six Sigma that focuses on improving the quality of employee-customer encounters, especially in sales and service organizations. It aims to improve and reduce variability in engagement levels between employees and customers. Unlike Six Sigma which was developed for manufacturing, Human Sigma addresses improving productivity through people. It combines assessing and improving the employee-customer experience based on five rules, including managing employee and customer experiences together, recognizing that emotions drive interactions, and measuring and acting locally. Measuring Human Sigma involves asking employees and customers how interactions made them feel using engagement surveys with scoring. The Sigma Score summarizes the effectiveness of employee-customer encounters and their relationship to organizational performance.