![quota samples quota samples](https://images.deepai.org/django-summernote/2019-05-27/84e492d8-2cb7-4bba-bf44-df7aa4fd9b76.jpg)
Non-probability methods are often dismissed or criticized because they do not have the statistical foundations of probability methods. The most obvious advantage in non-probability sampling is clearly the ability to target particular groups of the population. Advantages and Disadvantages of Non-Probability Sampling Non-probability techniques therefore have to be used whenever there is no readily available and complete list of the population under investigation. Similarly, there is not a sampling frame easily available to researchers of all the elderly in a population. It should be possible to obtain a list of people who are official members of the team, but this is unlikely to comprise all supporters. For example, when researching football supporters, it is not feasible to obtain a list of names or addresses of people who attend games.
![quota samples quota samples](https://i.stack.imgur.com/d9ZkR.png)
There are, of course, many situations in which it is not possible to obtain a sampling frame. Probability samples are possible only when there is a complete and up-to-date list of the members (names and/or addresses) of the population under investigation. The main feature present in a probability sample, but generally absent in a non-probability sample, is a sampling frame. There are five main types of non-probability sample: convenience, purposive, quota, snowball, and self-selection. In a non-probability sample, some members of the population, compared to other members, have a greater but unknown chance of selection. When the researcher deems there is no of new information left to be collected, the process is concluded.Alison Galloway, in Encyclopedia of Social Measurement, 2005 Introduction Definition This is similar to judgmental sampling, in that it is entirely dependent upon the judgement of the researcher. Sequential sampling: A researcher tries to find as many relevant respondents as possible, with the only limit being the exhaustion of relevant respondents or resources. This strategy differs from purposive sampling in that the goal is to locate a collection of unusual, different, or peculiar respondents that are not representative of the larger population. The crucial feature is that each person or unit is connected with another through a direct or indirect linkage.ĭeviant case sampling: Deviant case sampling is similar to purposive sampling in that it is used to seek out respondents that differ from the dominant pattern or that differ from the predominant characteristics of other respondents. Snowball sampling: Snowball sampling is a method for effectively identifying and sampling the respondents in a network. The use of judgmental sampling is appropriate in three situations: (1) to select unique respondents who are especially informative (2) to select members of a difficult-to-reach, specialized population (3) to identify particular types of respondents for in-depth investigation. Purposive or judgmental sampling: This strategy is used in situations where a researcher believes some respondents may be more knowledgable than others, and requires an expert to use their judgment in selecting cases with that purpose in mind. The researcher than determines a quota to meet in gathering responses from those categories, and accomplishes this task using haphazard methods. Quota sampling: Requiring a slight modification of haphazard sampling, quota sampling involves a researcher to first identifying relevant categories of people (e.g.
![quota samples quota samples](https://d3i71xaburhd42.cloudfront.net/cccbcf6a8b651c0a8f2b996cd92ee7fb9acaf2a0/5-Table3-1.png)
Commonly encountered examples of haphazard sampling include person-on-the-street interviews and television interviews. This strategy can produce ineffective, highly unrepresentative samples and as a result is not recommended unless no other options are feasible. Haphazard, accidental, or convenience sampling: Identified by many names, this strategy involves a researcher haphazardly selecting potential respondents based solely on the convenience of access to them. The explanations that follow describe some common nonprobability sampling techniques, and are excerpted from, and based upon, Neuman (2007, 141-145). Instead, these nonprobabilistic strategies focus on the extent to which the sample chosen provides illuminating information on the phenomenon being studied. As a result, the sampling strategies employed are not concerned with, or designed to allow, generalization of the results to a wider population. Many qualitative research projects have an implicit goal of creating a deeper understanding of a critical issue.