In sample studies, we have to make a plan regarding the size of the sample, selection of the sample, collection of the sample data and preparation of the final results based on the sample study. The whole procedure involved is called the sample design. The term sample survey is used for a detailed study of the sample. In general, the term sample survey is used for any study conducted on the sample taken from some real world data.
A complete list of all the units of the population is called the sampling frame. A unit of population is a relative term. If all the workers in a factory make a population, a single worker is a unit of the population. If all the factories in a country are being studied for some purpose, a single factory is a unit of the population of factories. The sampling frame contains all the units of the population. It is to be defined clearly as to which units are to be included in the frame. The frame provides a base for the selection of the sample.