Evidence map›Paper›PMID 18510722›Full record

ArticleBMC medical research methodology2008

Rasch fit statistics and sample size considerations for polytomous data.

Adam B Smith, Robert Rush, Lesley J Fallowfield, Galina Velikova, Michael Sharpe

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Article in BMC medical research methodology, 2008. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 137 papers.

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0cells of the map it votes in
137citing papers in PubMed
–field-weighted citation impact
1 · What the graph read from it

What it found

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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

137 citing papers in PubMed.

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  9. The adult social care outcomes toolkit easy read for older people (ASCOT-ER OP): an exploratory factor analysis and Rasch validation study.Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation · 2026
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  17. The Reduced Multi-Dimensional Health Literacy Scale: A First Bilingual Validation Using RASCH Analysis.International journal of environmental research and public health · 2025
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77 more citing papers are in PubMed but not listed here.

4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

5 authors.

Adam B SmithCancer Research UK - Clinical Centre, St, James's University Hospital, Leeds, UK. a.b.smith@leeds.ac.uk
Robert Rush
Lesley J Fallowfield
Galina Velikova
Michael Sharpe

Funding

Cancer Research UK
6 · The paper itself

Abstract

backgroundPrevious research on educational data has demonstrated that Rasch fit statistics (mean squares and t-statistics) are highly susceptible to sample size variation for dichotomously scored rating data, although little is known about this relationship for polytomous data. These statistics help inform researchers about how well items fit to a unidimensional latent trait, and are an important adjunct to modern psychometrics. Given the increasing use of Rasch models in health research the purpose of this study was therefore to explore the relationship between fit statistics and sample size for polytomous data.

methodsData were collated from a heterogeneous sample of cancer patients (n = 4072) who had completed both the Patient Health Questionnaire - 9 and the Hospital Anxiety and Depression Scale. Ten samples were drawn with replacement for each of eight sample sizes (n = 25 to n = 3200). The Rating and Partial Credit Models were applied and the mean square and t-fit statistics (infit/outfit) derived for each model.

resultsThe results demonstrated that t-statistics were highly sensitive to sample size, whereas mean square statistics remained relatively stable for polytomous data.

conclusionIt was concluded that mean square statistics were relatively independent of sample size for polytomous data and that misfit to the model could be identified using published recommended ranges.

Indexed as

Data Interpretation, StatisticalModels, StatisticalSample SizeAnxietyBiasDepressive DisorderFemaleHospitalizationHumansMaleMiddle AgedNeoplasmsPsychometricsReproducibility of ResultsSeverity of Illness IndexSurveys and Questionnaires

Identifiers

PMID18510722
PMCPMC2440760

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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.