sampling in qualitave research: insights from an … in qualitave research: insights from an...
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Samplinginqualita-veresearch:Insightsfromanoverviewofthemethodsliterature
Gentles, S. J., Charles, C., & Ploeg, J. (2015).The Qualitative Report, 20(11), 1772–1789.
Stephen Gentles TQR 7th Annual Conference January 16, 2016
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Outline
l Background & methods for review l Findings re 8 sampling-related topics l Emphasize 3 top findings
(conclusions re where clarity is lacking)
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WhatmakesQUALsamplingconfusing?
l DefineduniquelyinQUALl Mul1plemethodologicaltradi1ons,perspec1vesl Guidanceo?ennotclear,consistent&comprehensivel Difficultysearching&retrievingmethodsliterature
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à Systematic methods overview
l PhD comprehensives project l Combine expertise (reviews) & interest (methods) l No guidelines l Attention to developing & recording methods
Ø Methods publication: principles and strategies
l Useful for other “methods overviews”
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Literature identification & selection
Course'outlines'+'Input'from'6'experts'
Author'&'Publica:on'Short<list' Bibliometrics'&'Google'Scholar'publica:on'lists'
• Selected'“influen:al'authors”'• Iden:fied'publica:ons'
Obtain'and'review'full<text'of'each'
• H<index'scores'of'authors'• Number'of'cites'to'publica:ons'
• All':tles'by'author'reviewed'
Final'selec:on'criteria'
Publica:ons'selected'for'inclusion'
References'to'other'publica:ons'
• To'consider'less'influen:al'authors’'publica:ons'
Inclusion'criteria:'English'only;'methods'pubs.'(excl'1°'research'reports);'original'contribu:on;'≥1'paragraph'discussing'sampling'
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Progressive steps in the analysis
• Conclusions*aligned*with*goals*of*review*
!Final!
Analysis!• Narra6ves,*organized*by*key*topic*&*tradi6on*• Descrip6ve*summaries*&*comparisons*
• Derived*from*and*supported*by*matrices*• Note*areas*lacking*clarity,*consistency,*comprehensiveness*
Narra,ve!Summaries!
• Tables*organized*by*key*topic*&*tradi6on*• Quotes*copied*from*abstrac6on*form*• As*descrip6ve*summaries*of*key*topics*
• Allow*analy6c*comparisons*Matrices!
• Select*&*type*relevant*passages*from*text*into*fields*of*form*
• Record*ini6al*analy6c*observa6ons*re:*paHerns,*gaps*
Data!Abstrac,on!
1!
2!
3!
4!
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Scope:Tradi-ons&sampling-relatedtopics
How8topicsvarybetween3researchtradi1ons:1. Groundedtheory2. Phenomenology3. Casestudy
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3methodologicaltradi-ons
l Groundedtheory:l Toexplainahumansocial-psychprocess;producesasubstan1vetheoryl Interviews,o?enotherdatatypesl Theore1calsampling,constantcomparison
l Phenomenology:l Todescribe(some1mesinterpret)aphenomenonologicalexperiencel Interviewsonlyl Analysismethodsderivedfromphilosophicalfounda1ons
l Casestudy:l Todescribeindepthone/smallnumberofcases(“oneamongothers”)l Mul1pledatatypesl Methods:generalqualita1ve,lessdefinedbyitsownmethods(Stake)
Excludes literature on general qualitative research methods.
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Publica-onsselectedforinclusion(24)
l Groundedtheory:l Charmaz, 2003, 2006, 2014; Clarke, 2005; Corbin & Strauss,
2008, 2015; Glaser, 1978, 1992, 1998; Glaser & Strauss, 1967; Schatzman & Strauss, 1973; Strauss & Corbin, 1998
l Phenomenology:l Cohen, Kahn, & Steeves, 2000; Colaizzi, 1978; Giorgi, 2009; van
Manen, 1997, 2014l Casestudy:
l Merriam, 2009; Stake, 1995, 2005, 2006; Yin, 2009, 2011, 2014
l Excludedfulltext(16):l Nothing new compared to more recent editions (8); negligible info
on sampling (7); primary research report (1)
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TopicsàQues-onsaboutsamplingQuestion Sampling-related topic
What is sampling?
• Definitions of sampling
How? • Sampling strategies • Purposeful sampling • Theoretical sampling
What is selected?
• Sampling units (people, sites, cases, etc)
How much?
• Saturation • Sample size
When? • Timing of sampling decisions (a priori vs ongoing)
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Definition of sampling
QUAL research (abstracted): “the selection of specific data sources from which data are collected to address the research objectives.” Merriam Webster: “the act, process, or technique of selecting a representative part of a population for the purpose of determining parameters or characteristics of the whole population.”
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Varia-onsbyresearchtradi-on
Grounded theory: What is selected in theoretical sampling is unclear or inconsistent between authors (ie, it may not simply be data sources)
Phenomenology: What is selected is restricted to people only (ie, a single type of data source)
Case study: What is selected includes cases in addition to data sources
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“Sampling” Its meaning and appropriateness contested!
“…use of the ‘sample’ portion of the term [ie, in purposive sampling] still risks misleading others into thinking that the case comes from some larger universe or population of like-cases, undesirably reigniting the specter of statistical generalization. The most desirable posture may be to avoid referring to any kind of sample (purposive or otherwise).” —Yin, 2014, p. 42 Generalizes to populations vs Analytic generalizability
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Usageof“samplingstrategy”Authors who use term “sampling strategy”
Alternative terms
Grounded theory
• only Charmaz ~ method, ~ technique, form of ~, data gathering strategy
Pheno-menology
- method of choosing a sample, approach to ~
Case study • Yin • Merriam • Stake
kind of ~
à “Sampling strategy” language not used in all qualitative research traditions.
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“Purposeful/purposivesampling”
Case study
• Example inconsistency: Yin (2011): “Purposive sampling differs from several other kinds of sampling, snowball sampling, and random sampling.”
à Merriam (2009) includes snowball sampling
• Almostnomen1oninGT,phenomenology• Inconsistencyaboutwhatqualifiesaspurposeful/purposivesamplingincasestudy
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“Purposeful/purposivesampling”–broaderliterature
General qual. methods
• Numerous descriptions besides Patton (1980-2015) • “Purposeful” challenged as arbitrary (LeCompte, 1993)
Ø “All sampling is done with some purpose in mind” (Guba, 1985).
• Termfraughtwithambiguity,inconsistencies• PrecludesestablishingacommonlanguageàResearcherscannotsimplystatesamplingwaspurposeful,butmustspecifyhow
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Theore-calsampling
§ Specifictogroundedtheory§ WithinGT,consensusonimportantaspectsofdefini1on:
Aprocesswheredatagatheringisguidedbytheevolvingtheory,andtheaimistodevelopcategoriesintermsoftheirproper1esanddimensionsandtointegratethosecategories(ie,relatethemtoeachother)withinthetheory
§ OutsideGT,thedefini1ono?enover-simplified
à Its specific definition sometimes misrepresented in secondary sources.
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Samplingunits(Whatisselected?)Phenomenology • Data source (1 type):
Ø PeopleCase study Ø Cases –AND–
Ø Multiple data sources within the case: • People, sites, documents, etc.
Grounded theory • Unclear & inconsistent: Ø Data sources? –OR– Ø Examples of concepts*? –OR– BOTH?
*specific pieces of illustrative data (whatever their source)
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Satura-on(men1onedonlyonceincasestudy)
§ Cohen(2000):Reachingapointwhere“nothingnew”isencounteredusuallydoesn’thappeninphenomenology.
§ VanManen(2014):“Datasatura1on”irrelevanttophenomenology
Theore-calsatura-on—specificdefini-on§ Glaser&Strauss(1967):“…noaddi'onaldataarebeingfound
wherebythesociologistcandevelopproper'esofthecategory.”§ Charmaz(2006):Itis“notthesameaswitnessingrepe''onofthe
sameeventsorstories.…Thecommonuseofthetermsatura'onreferstonothingnewhappening.”
à Theoretical saturation differs from data saturation.
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Samplesize
l Satura'onarbitrarypost-hoccriterionforsufficientSSl ImpossibletospecifySSapriori
– YetSSes1matesnecessaryforproposals
Flexible SS estimates suggested by authors
Grounded theory
Charmaz(2006):Atleast25interviews
Phenome-nology Cohen(2000;forhermeneu1c):<10ifintense,≥30iflessintense
Colaizzi(2009;fordescrip1ve):around12par-cipantsCase study Yin(2011):25-50“units”(datasourceswithinasinglecase)
Stake(2005):4-10cases(formul1plecasestudy)
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Timingofsamplingdecisions
Apriori:Wherethedecisionsaboutwhattoselectaremadebeforedatacollec1on.
Ongoing:Wherethedecisionsaboutwhattoselectaremadea?erorinresponsetodatacollec1on.Either:Whereeither,andsome1mesboth,aprioriorongoingsamplingdecisionsmaybeinvolved.
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Ongoingtypesofsampling
Grounded theory (major)
• Theore-calsampling
Phenomenology (less emphasized)
• Two-1ersystemofsampling(Cohen,2000)
Case study (less emphasized)
• Snowballsampling(Merriam,2009;Yin2011)• Decidingonissuesforthequintain(Stake,2005b)• Theore1calsampling=ongoingsampling(Merriam,2009)
- usedto“samplewithinthecase”
à Ongoing sampling is less emphasized in phenomenology or case study.
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ApriorisamplingGrounded theory • Allauthors(exceptGlaser)acceptitforGT
• OnlyCharmazconsidershowPhenomenology • Timingofsamplingdecisionsrarelyspecified
• Adequatedescrip1onsofhowarelackingCase study • Timingofsamplingdecisionsrarelyspecified
• Adequatedescrip1onsofhowarelacking
• Tobetrulyapriori,criteria-basedpurposefulsamplingstrategies(eg,typicalcase,extremecase,maxvaria1on)requiresamplingframes&preliminarydata.
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Conclusions
1. Meaning and appropriateness of the term sampling in qualitative research is contested.
2. The language of purposeful sampling strategies is fraught with ambiguity and used inconsistently.
3. What is selected (sampling unit) in theoretical sampling is unclear: data sources or examples of concepts/categories or both?
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Questions - discussion…
Stephen Gentles, [email protected] Postdoctoral fellow CanChild Centre for Childhood Disability Research McMaster University, Hamilton, Ontario, Canada
Acknowledgements: • Cathy Charles • Ann McKibbon • Jenny Ploeg