The development of estimators of population parameters based on two-phase sampling schemes has seen a dramatic increase in the past decade. Various authors have developed estimators of population using either one or two auxiliary variables. The present volume is a comprehensive collection of estimators available in single and two phase sampling. The book covers estimators which utilize information on single, two and multiple auxiliary variables of both quantitative and qualitative nature. The estimators discussed in the text are based upon different mechanisms of the availability of auxiliary information, termed here as Full, Partial and No Information. Multivariate estimators in survey sampling are also discussed in the book. Two Phase Sampling will prove an invaluable point of reference for researchers working in the field of survey sampling in general and in the field of two-phase sampling in particular.