ArticleBMC medical research methodology2015
Sample size calculations for skewed distributions.
Article in BMC medical research methodology, 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 9 papers.
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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.
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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.
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Who cites it
9 citing papers in PubMed.
- Neonatal resuscitation using a laryngeal mask airway: a randomised trial in Uganda.Archives of disease in childhood · 2018Trial
- Analyzing Fatal Police Shootings: The Roles of Social Vulnerability, Race, and Place in the U.S.American journal of preventive medicine · 2025Article
- Evaluating the Cauchy combination test for count data.PloS one · 2025Article
- There was no call for immediate implementation of "Tetris" in clinical practice: Response to the commentary by Halvorsen et al. (2024).Molecular psychiatry · 2025Article
- Performance of administrative database frailty instruments in predicting clinical outcomes and cost for patients undergoing transcatheter aortic valve implantation: a historical cohort study.Canadian journal of anaesthesia = Journal canadien d'anesthesie · 2023Article
- Proactive expert system intervention to prevent or quit at-risk alcohol use (PRINT): study protocol of a randomized controlled trial.BMC public health · 2018Article
- Home versus hospital immunoglobulin treatment for autoimmune neuropathies: A cost minimization analysis.Brain and behavior · 2018Article
- Sample size calculations based on a difference in medians for positively skewed outcomes in health care studies.BMC medical research methodology · 2017Article
- Protocol for assessing maternal, environmental and epigenetic risk factors for dental caries in children.BMC oral health · 2015Article
Corrections and comments
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Authors and funding
2 authors.
Funding
Abstract
backgroundSample size calculations should correspond to the intended method of analysis. Nevertheless, for non-normal distributions, they are often done on the basis of normal approximations, even when the data are to be analysed using generalized linear models (GLMs).
methodsFor the case of comparison of two means, we use GLM theory to derive sample size formulae, with particular cases being the negative binomial, Poisson, binomial, and gamma families. By simulation we estimate the performance of normal approximations, which, via the identity link, are special cases of our approach, and for common link functions such as the log. The negative binomial and gamma scenarios are motivated by examples in hookworm vaccine trials and insecticide-treated materials, respectively.
resultsCalculations on the link function (log) scale work well for the negative binomial and gamma scenarios examined and are often superior to the normal approximations. However, they have little advantage for the Poisson and binomial distributions.
conclusionsThe proposed method is suitable for sample size calculations for comparisons of means of highly skewed outcome variables.
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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.