This document discusses sampling methods for statistical analysis. There are two main methods of collecting data: census, which studies the entire population, and sampling, which studies a subset of the population. Sampling is useful because it saves time and costs compared to a census, and results can be more reliable. There are two types of sampling: probability sampling, where items are selected randomly, and non-probability sampling, where selection is non-random. Some examples of probability sampling methods provided are simple random sampling, systematic sampling, stratified sampling, cluster sampling, and multi-stage sampling. Non-probability methods include judgment sampling, quota sampling and convenience sampling. The document defines key sampling terminology and discusses sampling error.