This document discusses sampling methods used in statistics. It defines sampling as making inferences about a whole population by examining a subset of selected units. The main purposes of sampling are to provide statistical information about a population more efficiently and accurately than a complete census. Probability sampling methods like simple random sampling, stratified random sampling, and systematic random sampling aim to give all population units an equal chance of selection. Non-probability methods like convenience sampling and judgmental sampling do not use random selection. The document also outlines different sampling types and the steps involved in the sampling process.