The goal of a census the goal of a census is to determine type, diversity, and distribution of a population within a research area. A substantial sample size is necessary for accurate data analysis.

The goal of Existing sources ( I have not gotten to this one yet)

Survey sampling the principal goal of survey sampling is the Estimation of finite population parameters. The real issue, however, is not whether the population can be viewed as large, but whether the sample can. It is precisely because samples are often very large in survey sampling, that the apparently exclusive use of randomization methods dominated its practice for so long.

The goal of designed experiments is to determine which factors are important with respect to location and scale. A ranked list of the important factors is also often of interest