Determining Sample Design:
All the items consideration in any field of inquiry constitute a universe or population. A complete enumeration of all the items in the population is known as a census inquiry. In such an inquiry when all the items are covered no element of chance is left and highest accuracy is obtained. But in practice this may not be true. This type of inquiry involves a great deal of time money and energy. Not only this census inquiry is not possible in practice under many circumstances.
The researcher must decide the way of selecting sample or the sample design. A sample design is a definite plan determined before any data are actually collected for obtaining a sample from a given population. Samples can be either probability samples or non probability sample with probability samples each element has a known probability of beings included in the sample but the non probability samples do not allow the research to determine this probability.