theoretical sampling - In a grounded theory study, a strategy of choosing data sources that are most
likely to help a researcher develop a theory of the phenomenon under investigation.
discriminant sampling - In a grounded theory study, a follow-up to theoretical sampling in which a
researcher identifies one or more data sources that might help substantiate an emerging theory of the
phenomenon under investigation.
extreme case sampling - Type of purposive sampling that involves focusing on particular cases or
individuals determined to be unusual and atypical, or to represent extreme examples; most often used
in qualitative (rather than quantitative) research.
convenience sampling - Approach to sampling that entails using readily available research sites and/or
easily accessible individuals who can provide insights related to central research questions.
snowball sampling - In qualitative research, a method of identifying participants that involves asking
existing participants to refer or recruit other individuals (e.g., colleagues or acquaintances) who also
have experiences and knowledge relevant to the topic under study.
replicable - Describing a study whose results have been reproduced when the study was repeated, or
replicated. Also called reproducible. See also conceptual replication, direct replication, replication-plus-
extension.
In direct replication, researchers repeat an original study as closely as they can to see whether the effect
is the same in the newly collected data.
In a conceptual replication, researchers explore the same research question but use different
procedures. The conceptual variables in the study are the same, but the procedures for operationalizing
the variables are different.
In a replication-plus-extension study, researchers replicate their original experiment and add variables
to test additional questions.
Sometimes researchers collect all the studies on a topic and consider them together—generating what is
known as a review article, or a literature review.
