This book is intended both as a text and as a reference source for researchers and practitioners in estimation theory, information theory, multi group analysis, measurement models, customer satisfaction index and service of quality. For this purpose, an up to date comprehensive bibliography on this topic has been included There are few books introduce the idea of generalized maximum entropy. This book; based on some of my published articles with my colleagues and former students, is consider as the first monograph to combine between two new statistical subjects, customer satisfaction and generalized maximum entropy. It takes the reader step-by-step to understand the generalized maximum entropy as a new estimation method from a simple linear model to measurement error models; the so called errors-in- variables models; then achieving more complicated linear structural relationships.