Sample size in qualitative interview studies: guided by information power

TY - JOUR

T1 - Sample size in qualitative interview studies

T2 - guided by information power

AU - Malterud, Kirsti

AU - Siersma, Volkert Dirk

AU - Guassora, Ann Dorrit Kristiane

PY - 2016/11/1

Y1 - 2016/11/1

N2 - Sample sizes must be ascertained in qualitative studies like in quantitative studies but not by the same means. The prevailing concept for sample size in qualitative studies is “saturation.” Saturation is closely tied to a specific methodology, and the term is inconsistently applied. We propose the concept “information power” to guide adequate sample size for qualitative studies. Information power indicates that the more information the sample holds, relevant for the actual study, the lower amount of participants is needed. We suggest that the size of a sample with sufficient information power depends on (a) the aim of the study, (b) sample specificity, (c) use of established theory, (d) quality of dialogue, and (e) analysis strategy. We present a model where these elements of information and their relevant dimensions are related to information power. Application of this model in the planning and during data collection of a qualitative study is discussed.

AB - Sample sizes must be ascertained in qualitative studies like in quantitative studies but not by the same means. The prevailing concept for sample size in qualitative studies is “saturation.” Saturation is closely tied to a specific methodology, and the term is inconsistently applied. We propose the concept “information power” to guide adequate sample size for qualitative studies. Information power indicates that the more information the sample holds, relevant for the actual study, the lower amount of participants is needed. We suggest that the size of a sample with sufficient information power depends on (a) the aim of the study, (b) sample specificity, (c) use of established theory, (d) quality of dialogue, and (e) analysis strategy. We present a model where these elements of information and their relevant dimensions are related to information power. Application of this model in the planning and during data collection of a qualitative study is discussed.

U2 - 10.1177/1049732315617444

DO - 10.1177/1049732315617444

M3 - Journal article

C2 - 26613970

SN - 1049-7323

VL - 26

SP - 1753

EP - 1760

JO - Qualitative Health Research

JF - Qualitative Health Research

IS - 13

ER -