Census and survey data are two important sources of information used in data analysis, research, planning and policy-making. Both provide information about a population, but they differ mainly in the way data are collected, the coverage of the population, the purpose of data collection and the resources required. A clear understanding of these differences is important because the choice between census and survey affects the quality, cost and usefulness of statistical analysis. A census is a complete enumeration of all units or members of a defined population. In a population census, information is collected from every individual or household belonging to the population under study. For example, the Population Census of India attempts to collect demographic, social and economic information about the population. Similarly, an agricultural census may collect information from all relevant agricultural holdings within its defined scope. Since every unit is included, a census can provide comprehensive information about the entire population. A survey, on the other hand, collects information from only a part of the population, usually called a sample. The sample is selected according to a suitable sampling method so that it represents the larger population. For example, if a researcher wants to study the employment situation of students in a large university, it may not be necessary to collect information from every student. A properly selected sample of students can provide useful information about the whole student population. Surveys are therefore widely used in social science, economics, market research, health studies and many other fields. The first major difference between census and survey data is coverage. Census data cover every unit of the population within the defined scope, whereas survey data cover only selected units. Therefore, census provides complete population-level information, while a survey provides