Health Services Research Unit, University of Aberdeen, Aberdeen, UK.
Psychol Health. 2010 Dec;25(10):1229-45. doi: 10.1080/08870440903194015.
In interview studies, sample size is often justified by interviewing participants until reaching 'data saturation'. However, there is no agreed method of establishing this. We propose principles for deciding saturation in theory-based interview studies (where conceptual categories are pre-established by existing theory). First, specify a minimum sample size for initial analysis (initial analysis sample). Second, specify how many more interviews will be conducted without new ideas emerging (stopping criterion). We demonstrate these principles in two studies, based on the theory of planned behaviour, designed to identify three belief categories (Behavioural, Normative and Control), using an initial analysis sample of 10 and stopping criterion of 3. Study 1 (retrospective analysis of existing data) identified 84 shared beliefs of 14 general medical practitioners about managing patients with sore throat without prescribing antibiotics. The criterion for saturation was achieved for Normative beliefs but not for other beliefs or studywise saturation. In Study 2 (prospective analysis), 17 relatives of people with Paget's disease of the bone reported 44 shared beliefs about taking genetic testing. Studywise data saturation was achieved at interview 17. We propose specification of these principles for reporting data saturation in theory-based interview studies. The principles may be adaptable for other types of studies.
在访谈研究中，通常通过采访参与者直到达到“数据饱和”来证明样本量的合理性。然而，目前还没有达成共识的确定方法。我们提出了基于理论的访谈研究中确定饱和的原则（在这种研究中，概念类别是通过现有理论预先确定的）。首先，为初始分析指定最小样本量（初始分析样本）。其次，指定在没有新想法出现的情况下将进行多少更多的访谈（停止标准）。我们在两项基于计划行为理论的研究中展示了这些原则，旨在确定三种信念类别（行为、规范和控制），初始分析样本为 10，停止标准为 3。研究 1（对现有数据的回顾性分析）确定了 14 名普通内科医生关于管理不使用抗生素的咽痛患者的 84 个共同信念。规范信念的饱和标准得到了满足，但其他信念或研究范围内的饱和标准没有得到满足。在研究 2（前瞻性分析）中，17 名佩吉特病患者的亲属报告了 44 个关于接受基因检测的共同信念。在第 17 次访谈时，研究范围内的数据饱和得到了满足。我们建议在基于理论的访谈研究中报告数据饱和时指定这些原则。这些原则可能适用于其他类型的研究。
