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Extreme of deviant case sampling
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Learning from highly unusual manifestations of the phenomenon of interest
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Focusing on how things should be or could be, rather than how things are Suitable for realist syntheses
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Intensity sampling
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Information-rich cases that manifest the phenomenon intensely, but not extremely, such as good students/ poor students, above average/below average.
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To develop a comprehensive understanding of the phenomena that is been researched in the synthesis
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Maximum variation sampling
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identifying key dimensions of variations and then finding cases that vary from each other as much as possible.
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To identify essential features and variable features of a phenomenon among varied contexts
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Identifies important patterns that cut across variations
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To construct an holistic understanding of the phenomenon
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Homogenous sampling
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Picking a small, homogeneous sample. Reduces variation, simplifies analysis, facilitates group interviewing
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To overcome the critique of “mixing apples and oranges”:i.e. to overcome the epistemological incommensurability of different qualitative methods
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To describe some particular subgroup in-depth
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Suitable for participatory syntheses
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Typical case sampling
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Illustrates or highlights what is typical, normal, average
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To study how common themes recurring in the published literature might be related to the relative strengths and weaknesses of the typical methodologies or theories underpinning the typical studies
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Critical case sampling
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Permits logical generalization and maxi-mum application of information to other cases
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To assist stakeholders in making informed decisions about the viability of a certain innovation
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Snowball sampling
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Seeking information from key informants about details of other information-rich cases in the field
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To identify studies that are highly valued by different stakeholders
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To identify studies outside the academic mainstream
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Criterion sampling
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Selecting all cases that meet some predetermined criterion of importance
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To construct a comprehensive understanding of all the studies that meet certain pre-determined criteria
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Theoretical sampling
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Selecting cases that represent important theoretical constructs about the phenomenon of interest
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Research synthesis who employ constant comparative methods or grounded –theory approaches
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Confirming sampling
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Selecting cases that are additional examples that fit already emergent patterns; these cases
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To advocate a particular stance for ethical, moral and/or political reasons
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Suitable for openly ideological synthesis
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Disconfirming sampling
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Selecting cases that do not fit. They are a source of rival interpretations as well as a way of placing boundaries around confirmed findings
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To shake our complacent acceptance of popular myths and generalizations in a field
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Stratified purposeful sampling
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Sampling within samples where each stratum is fairly homogeneous
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To examine variations in the manifestation of a phenomenon as any key factor associated with the phenomenon is varied. In a research synthesis, this factor may be contextual, methodological, or conceptual.
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Opportunistic sampling
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Adding cases to a sample to take advantage of unforeseen opportunities after fieldwork has begun
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To be used in a research area which is at its exploratory stage or when the synthesis does not have an insider status in the relevant field of research
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Suitable to participatory syntheses where the synthesis purpose evolves in response to the changing needs of the participant co-synthesists
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Purposeful random sampling
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Adds credibility to sample when potential purposeful sample is larger than one can handle. Reduces judgment within a purposeful category
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To locate most of the primary research reported on a topic and then randomly select a few reports from this pool for in-depth discussion
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Sampling politically important cases
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Selecting a politically sensitive site or unit of analysis
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To gain attention of different stakeholders and the synthesis findings get used.
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Suitable for synthesis of hot topics, in which several stakeholders are interested
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Convenience sampling
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Involve selecting cases that are easy to access and inexpensive to study
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Not a recommendable technique, because its neither purposeful, nor strategic
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Combination or mixed purposeful sampling
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To use a combination of two or more sampling strategies to select evidence that adequately addresses their purpose
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To facilitate triangulation and flexibility in meeting the needs of multiple stakeholders
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