PURPOSIVE SAMPLING
What is Purposive Sampling?
Kerlinger (1986) explained purposive sampling as another type of non-probability sampling, which is characterized by the use of judgment and a deliberate effort to obtain representative samples by including typical areas or groups in the sample.
A purposive sample is one in which a surveyor tries to create a representative sample without sampling at random.
In other words, Purposive sampling targets a particular group of people. When the desired population for the study is rare or very difficult to locate and recruit for a study.
For example: To study the life style of the young children of the 
construction workers near the construction site.It restricts the sample population to a very specific population and then tends to use all of the subjects available.
The power of purposive sampling lies in selecting information rich-cases, for in-depth analysis related to the central issues being studied.
Purposive sampling can be done in addition to probability sampling also.
For example: after completing your baseline study based on a random sample, you may recognize that certain sections of the project area are quite different from other areas due to variations in landscape, geography, culture etc.
You may then purposively select those areas to get representative information about how the variations have influenced the behavior of the people.
Uses for purposive sampling
- Validation of a test or instrument with a known population
- Collection of exploratory data from an unusual population
- Geographical areas to represent a larger area
One of the commonest uses of purposive sampling is in selecting a group of geographical areas to represent a larger area.
For example: door-to-door interviewing can become extremely expensive in rural areas with a high population density. In a country such as India, it is not feasible to do a door-to-door survey covering the whole country. Though areas could be picked purely at random, if the budget was small and only a small number of towns and cities could be included, you might choose these in a purposive way, perhaps ensuring that different types of town were included.
Advantages
It is easy to undertake.
Disadvantages
It has a potential for inaccuracy in the researcher’s criteria and resulting sample selections.
Conclusion
In short, purposive sampling is best used with small numbers of individuals/groups which may well be sufficient for understanding human perceptions, problems, needs, behaviors and contexts, which are the main justification for a qualitative audience research.
Purposive sampling
References:
http://www.okstate.edu/ag/agedcm4h/academic/aged5980a/5980/newpage15.htm
http://www.wadsworth.com/psychology_d/templates/student_resources/workshops/res_methd/sampling/sampling_30.html
http://jan.ucc.nau.edu/~mezza/nur390/Mod3/sampling/lesson.html
http://www83.homepage.villanova.edu/richard.jacobs/EDU%208603/lessons/sampling.ppt#1
Mini Quiz
1. Purposive sampling is another type of probability sampling.
2. Purposive sampling does not require the researcher to describe in detailed methods used to select a sample.
3. It is possible to define purposive sample because the researcher uses clear criteria (e.g. experience & prior knowledge) to identify criteria for selecting the sample.
