Assignment 5 Essay Example | Topics and Well Written Essays - 1500 words - 3

Assignment 5 - Essay Example probability and non-probability sampling design arises because of the use of random sampling under probability-based sampling (Gravetter & Wallanau, 2008). Probability sampling works on the principle random sampling such that every unit in a population has equal chance of being selected as a sampling unit. However, under non-probability sampling, sampling units are selected on any other basis but not based on selected randomly. Systematic random sampling involves the design of sample in which samples are drawn in some systematic manner. For instance, every fifth item from a number wise population should be selected as a sampling unit, etc. Cluster random sampling divides the population based on geographical area and then the random samples are drawn from each cluster. Geographical area is the main distinguishing factor between cluster and stratified random sampling design. Any other method of drawing samples from a given population other than random sampling is referred to as non-probability sampling. Generally, there are two broader categories of non-probability sampling such as convenience sampling and purposive sampling. Purposive sampling itself has further five types and discussed in the subsequent paragraphs. Under convenience sampling, the researcher draws the sample as per his/her own convenience. For instance, researchers conducting social research use college or university students as their target samples because it is easy to collect their responses. In clinical researches, patients are the major respondents of the researcher because it is easy to obtain their responses. However, the biggest problem that lies with this method is that the samples drawn are not actually the true reflection of population and thus creates the threat to external validity of the research design. Purposive sampling mainly involves the selection of sampling units based on some purpose behind their selection. This method is the best method of sampling in case where the