ABSTRACT
The present chapter spells out the need for data in both empirical and theoretical research, nature and sources of data, types of data – cross-sectional vs. longitudinal, mechanisms for data collection, viz. sample surveys and designed experiments for prospective data collection along with quasi-experiments for retrospectively collected data to be taken care of and data integration to get a unified picture from several disparate sources of data. For sample surveys and designs of experiments, the chapter indicates the limitations of different survey methods and experimental designs and the decisions to be taken by the research worker to make the right uses of the known concepts, methods and tools. Thus appropriate decisions on sampling units and sampling frame, variable(s) and parameter(s) of interest, sample size and allocation problems have to be resolved. Similarly, the choice of factors and their levels, and of the response variable(s) and number of runs or replications of the experiment have also to be decided upon.
