BackgroundChoosing a suitable sample size in qualitative research is an area of conceptual debate and practical uncertainty. That sample size principles, guidelines and tools have been developed to enable researchers to set, and justify the acceptability of, their sample size is an indication that the issue constitutes an important marker of the quality of qualitative research. Nevertheless, research shows that sample size sufficiency reporting is often poor, if not absent, across a range of disciplinary fields.MethodsA systematic analysis of single-interview-per-participant designs within three health-related journals from the disciplines of psychology, sociology and medicine, over a 15-year period, was conducted to examine whether and how sample sizes were justified and how sample size was characterised and discussed by authors. Data pertinent to sample size were extracted and analysed using qualitative and quantitative analytic techniques.ResultsOur findings demonstrate that provision of sample size justifications in qualitative health research is limited; is not contingent on the number of interviews; and relates to the journal of publication. Defence of sample size was most frequently supported across all three journals with reference to the principle of saturation and to pragmatic considerations. Qualitative sample sizes were predominantly – and often without justification – characterised as insufficient (i.e., ‘small’) and discussed in the context of study limitations. Sample size insufficiency was seen to threaten the validity and generalizability of studies’ results, with the latter being frequently conceived in nomothetic terms.ConclusionsWe recommend, firstly, that qualitative health researchers be more transparent about evaluations of their sample size sufficiency, situating these within broader and more encompassing assessments of data adequacy. Secondly, we invite researchers critically to consider how saturation parameters found in prior methodological studies and sample size community norms might best inform, and apply to, their own project and encourage that data adequacy is best appraised with reference to features that are intrinsic to the study at hand. Finally, those reviewing papers have a vital role in supporting and encouraging transparent study-specific reporting.Electronic supplementary materialThe online version of this article (10.1186/s12874-018-0594-7) contains supplementary material, which is available to authorized users.

Seventy six senior academics from 11 countries invite The BMJ’s editors to reconsider their policy of rejecting qualitative research on the grounds of low priority. They challenge the journal to develop a proactive, scholarly, and pluralist approach to research that aligns with its stated mission

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This position paper argues that the lack of take-up of management science (MS)

One limitation on high resolution laser spectroscopy lies in establishing a reliable frequency scale. We report an offsetlocked heterodyne spectrometer employing two cw tunable dye lasers, which has a fast response, frequency agility, and an absolute accuracy in the kilohertz range. The application of this device has been demonstrated by exploring the hyperfine structure of the sodium D1 line. The splitting of the %, , , ground state, which was already known from radio frequency measurements, was determined as a check of correct operation. A new measurement was made of the splitting of the P,,, excited state.A schematic layout of the spectrometer is shown in Fig. 1. It used two Spectra-Physics Model 380 ring dye lasers. One dye laser (the master laser) was frequency-locked by conventional methods to an atomic reference utilising saturated absorption in a sodium vapour cell.Part of the output beam from the other (slave) laser was carefully aligned collinearly with a fraction of the beam from the master laser so that heterodyne beats between the two could be detected by a wide-bandwidth photodiode. The heterodyne beat signal was mixed with the output of a computer-controlled microwave synthesizer to produce a downconverted intermediate frequency centrrd on 297.520 MHZ. After amplification with automatic gain control this intermediate frequency was directly counted in a fast-sampling digital counter, from which was generated an analogue error signal that was used to close the loop. bocklng loop i * -m SlOX servo D.A.C QTuD3 Fig. 1. A block schematic diagram of the offset-locked laser heterodyne spectrometer is shown. Laser beams are shown by dashed l i e s and electronic connections by solid lies. Optical beam splitters are denoted by BS and the 20 GHz bandwidth photodiode by PD. Overall the loop was robust, recovering automatically from mode hops, and was frequency-agile. Standard deviations of intermediate frequency samples showed fluctuations of 1.4 kHz over an averaging time of 2.0 s, and 30 kHz over 20 ms.A conventional sodium atomic beam, collimated to give a line width close to the natural width, was excited by the slave laser and the spectral features were observed by resonance fluorescence.' Frequency splittiigs were investigated by two methods, linear scans and a frquency-agile technique, in which the slave laser repeatedly hopped from side to side of a line. The centroid of any spectral component could be readily determined. A calibration run on the ground state splitting yielded 1.771624(5) GHz to be compared with a radio frequency measuremen? gave 1.771626188(10) GHz. The new value determined for the excited state splitting was 188.813(3) MHZ.