Collecting quality information/data is a prerequisite of any research program. And there are mainly two different methods of collecting data: (a) census method and (b) sample survey method. In census method, data are collected from individual members of the population. On the other hand, in sample survey method, information is collected from the units of sample drawn for the purpose following definite methods of the sampling techniques. A comparative account of two methods of data collection is given in Table 6.1.