Purposive Sampling Strategy and Its Sample Size

PurposiveSampling Strategy and Its Sample Size


PurposiveSampling Strategy and Its Sample Size

APurposive Sampling method is the most appropriate sampling strategyfor a qualitative research method. The use of a purposive samplingstrategy is seen when a qualitative researcher chooses a specificsample within the population to use for a particular research project(Teddlie &amp Yu, 2011, p. 77-100). Different from random studiesthat may intentionally deliberately involve a diverse cross-sectionof cultures, ages, and backgrounds, purposive sampling strategy willhelp the researcher to focus on samples with particularcharacteristics. The individual characteristics will assist theresearcher in conducting a relevant study. Therefore, a qualitativeresearch study would benefit when a researcher decides to use thePurposive Sampling Strategy. Purposive research has the qualitiesthat it takes to conduct a proper qualitative research (Ritchie etal., 2013). In a purposive sampling strategy, a subject that has someparticular characteristics will be used. Ritchie and others proposedsome cases of purposive sampling. Purposive sampling is one the mostacceptable research strategy in qualitative research.

Thequalitative researcher may decide to employ some of the commonly usedpurposive sampling strategies. The sampling plan methods include:

MaximumVariation Sampling(MVS) MVS will be seeking to address the subject of study from manyviewpoints thereby will help the researcher in understanding theissues that he will be studying. MVS will be involving manycandidates in the target whole of the target population that will berelating to the topic of the study. For example, in case theresearcher will be researching on an educational program, he/she willinvolve students that hate the educational program and the studentsthat will be excelling in school.

Extremeor Deviant Case Samplingthis is a sampling that will be useful for the qualitative researcheras it will enable him/her to concentrate on samples that will beunusual or typical. The extreme method of sampling will be mostlyapplied while the researcher will be developing policies andregulations that will guide the research practices and regulationsthat will guide the research practice on the dos and dons of thewhole research process (Suri, 2011, p. 63-75). Extreme samplingmethod would be useful in looking for variations in the cases understudy to explain why their recoveries would be typical.

CriticalCase Samplingthis is a method that will be useful in the initial stages of thequalitative research that would be necessary for determining whetheror not a more in-depth studies will be warranted. Critical CaseSampling will also be of use to determine whether the available fundsand other resources will be limited. Key case sampling will be amethod where selected numbers of significant qualities are chosen andcross-checked (Abrams, 2010, p. 536-550). A criterion that theresearcher will be using in deciding whether an issue or a subjectwill be critical will mostly follow the following statements: “Incase it happened there, would it happen anywhere?”

TotalPopulation Samplingthis is a sample method that work on the rationale that at some pointleaving out certain cases from a qualitative sampling might mean thata researcher would have an incomplete sampling. Besides, it couldimply that the obvious or significant pieces of the sampling are theones that could be left out. In the case of avoiding any mistake ofleaving out on significant bits of a population, the researcher will,therefore, decide on Total Population Sampling as the best option.Total Population Sampling would be used by the researcher in placesthat the number of cases to be investigated will be comparativelysmaller.

Factorsthat Contribute to the Choice of a Purposive Sampling Strategy

Purposivesampling will be a most appropriate strategy that would benefit thequalitative researcher. The purposive sampling has some advantagesthat would make it the best option for the qualitative research plan.

Benefitsof Purposive Sampling Strategy are that it will involve various typesof techniques. There are different types of purposive samplingmethods like homogenous sampling, critical case sampling, and expertsampling. Among the benefits of purposive sampling method will be itsability to collect large amounts of information by using a variety ofvarious techniques. The variety that the approach will offer will inturn give the researcher a better picture of the information aboutthe population under study.

Purposivesampling technique would also allow stage building blocks. Aqualitative research will mostly involve a series of differentphases each phase will be building from the original phase. In theprogression case, purposive sampling will be useful to the researcheras he/she will be able to use the variety of methods that will beavailable to build and raise the researched data. For instance, hewill start from a critical case stage sampling and use theinformation that he shall have attained to progress to the expertsampling stage.

Anotherfactor that would make the purposive sampling the best alternative isthe ability to study an extreme or deviant case. The researcher wouldbe in a position to learn from more unusual cases of the phenomenonthat would be of interest. The intensity of the information in apurposive sampling will also be of a greater advantage. Intensity –Information may be abundant in cases that would manifest thephenomenon under study intensely. Purposive Sampling will also giveroom for a maximum variation in the study. Intentionally picking thewide range of variations on dimensions that will be interesting tothe researcher will be of significance in the study.

Purposivesampling will be a better choice as it will ensure homogeneity in thequalitative study. The study will focus and reduce variations andsimplify the analysis of the data of the target population understudy. The sampling method will also allow the researcher to carryout a more stratified purposeful study. The study will beIllustrating characteristics of particular subgroups that will be ofinterest to the researcher facilitating comparisons. Some cases thatcritical in nature will also be addressed with ease through the useof the purposive sampling technique.

TheBest Sample Size for Purposive Sampling

Ina purposive sampling strategy, the researcher will choose a samplesize that is relatively smaller as he will be going to particulargroups with the desired qualities. The researcher will have thesubject of the study with a purpose in mind. Therefore, he/she wouldhave one or more particular predefined sets of groups and would gofor a sample size of not more than 30 cases. The researcher could belooking for a particular group or age bracket. In selecting a samplesize, one of the first things the researcher will do will be toverify that the respondents will be meeting the criteria for being inthe sample.

Factorsthat Lead to the Choice of the Sampling Size

Purposivesampling strategy will be very useful for situations where theresearcher will need to reach a targeted sample quickly. It couldalso be applicable where sampling selection will be forproportionality. Purposive sampling is a strategy that involves astudy that is seeking some specific cases and, therefore, is not atrial and error method. There will be no need for using a largesample size that would make the identification of the desiredqualities more difficult. The smaller the size of the sample is apurposive sampling, the higher the chances of accuracy in the study(Francis et al., 2010, p. 1229-1245).

Onewould argue that a purposive sampling is the best sampling strategy,as it will give the researcher an opportunity to come up with resultsthat are more accurate from a smaller sample. Qualitative samplinginvolves the use of observational techniques that would mostly beaccurate when using smaller sample sizes.

Theresearcher will also enjoy the opportunity of choosing the purposivesampling method that would be most appropriate for the study that hewill be conducting. The use of more than one sampling method is ofadvantage, as it will enable the researcher to view his study fromvarious angles and determine the right way that will give the bestfeedback. In the use of a purposive sampling strategy, chances oferror detection in the study will be high, as the research will becarried out in a sequential manner. Before the researcher woulddecide to move to the next stage from another, he could decide tocross check for a possibility of error and rectify it before it willtoo late.

Asampling that involves a smaller size will be able to study as theresearcher will have a better timing for observing various cases andtaking appropriates notes (Francis et al., 2010, p. 1229-1245). Whena sample size is much bigger, a researcher may spend lesser timeobserving cases under study hence taking incomplete or irrelevantnotes on what would paramount for the study.


Abrams,L. S. (2010). Sampling ‘Hard to Reach’Populations in QualitativeResearch The Case of Incarcerated Youth. Qualitative Social Work,9(4), 536-550.

Francis,J. J., Johnston, M., Robertson, C., Glidewell, L., Entwistle, V.,Eccles, M. P., &amp Grimshaw, J. M. (2010). What is an adequatesample size? Operationalising data saturation for theory-basedinterview studies. Psychology and Health, 25(10), 1229-1245.

Ritchie,J., Lewis, J., Nicholls, C. M., &amp Ormston, R. (Eds.). (2013).Qualitative research practice: A guide for social science studentsand researchers. Sage.

Suri,H. (2011). Purposeful sampling in qualitative research synthesis.Qualitative Research Journal, 11(2), 63-75.

Teddlie,C., &amp Yu, F. (2011). Mixed methods sampling a typology withexamples. Journal of mixed methods research, 1(1), 77-100.