Using a concept map explain the following a probability and

Using a concept map, explain the following:

a. probability and non-probability sampling designs.

b. Identify the Factors Affecting the Choice of Sampling Design

Solution

Part a)

Researchers gather information by variety of techniques, starting from the experimental designs used in the physical sciences to the surveys more common in the social sciences. Many of these methods of gathering information include a choice of experimental subject. For example, we may want to decide which of the patients to be examined in a medical study, or the respondents to be interviewed in a survey. This choice can be made using probability-based methods, where the choice is by some \"mechanical” phenominon involving lists of random numbers, or the equivalent. Alternatively, the choice may be made by other methods, invoking some component of judgement. Methods including judgement are sometimes referred to as purposive selection, judgement selection, or non-probability selection. In this generality, it is hard to say very much about the choice between probability and non-probability selection.

If probability-based sampling is properly carried out, there will be none of the bias that can arise from subjective judgements in sample selection. There is the possibility of such bias but not in quota samples. For example, interviewers may consciously or unconsciously select non-threatening or easy-to-approach respondents, or those who are easy to contact. The validity of the model underlying quota sampling might be open to question, and difficult to verify. With probability sampling, we use the randomisation distribution to decide from the sample, and to obtain sampling errors. In a quota sample, we cannot get comparable estimates of acuracy.

Part b)

When sampling, you need to decide which units/people/organizations to include in your sample and which ones to exclude. As you\'ll know by now, sampling techniques act as a guide to help you decide these units, and you will have chosen a specific probability or non-probability sampling technique: