How many do I need? Basic principles of sample size estimation

Journal of Advanced Nursing
Declan DevaneMike Clarke

Abstract

In conducting randomized trials, formal estimations of sample size are required to ensure that the probability of missing an important difference is small, to reduce unnecessary cost and to reduce wastage. Nevertheless, this aspect of research design often causes confusion for the novice researcher. This paper attempts to demystify the process of sample size estimation by explaining some of the basic concepts and issues to consider in determining appropriate sample sizes. Using a hypothetical two group, randomized trial as an example, we examine each of the basic issues that require consideration in estimating appropriate sample sizes. Issues discussed include: the ethics of randomized trials, the randomized trial, the null hypothesis, effect size, probability, significance level and type I error, and power and type II error. The paper concludes with examples of sample size estimations with varying effect size, power and alpha levels. Health care researchers should carefully consider each of the aspects inherent in sample size estimations. Such consideration is essential if care is to be based on sound evidence, which has been collected with due consideration of resource use, clinically important differences and the need to avo...Continue Reading

References

Sep 7, 1996·BMJ : British Medical Journal·D G Altman
May 7, 1997·Journal of the National Cancer Institute·D Machin, K W Andersen
Nov 7, 1998·BMJ : British Medical Journal·C Roberts, D Torgerson
Apr 30, 1999·BMJ : British Medical Journal·D G Altman, J M Bland
Dec 29, 2005·Evidence-based Cardiovascular Medicine·L Friedman

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Citations

Jul 26, 2005·Archives of Disease in Childhood·A K Akobeng
Mar 20, 2013·BMC Gastroenterology·Usama Ahmed AliUNKNOWN Dutch Pancreatitis Study Group
Oct 19, 2010·Indian Journal of Ophthalmology·Nithya J Gogtay
Mar 9, 2010·Australian Critical Care : Official Journal of the Confederation of Australian Critical Care Nurses·Jodie Kernick, Judy Magarey
Nov 11, 2008·European Journal of Obstetrics, Gynecology, and Reproductive Biology·Valerie SmithShane Higgins
Feb 9, 2007·Journal of Evaluation in Clinical Practice·Riitta SuhonenHesook Suzie Kim
Mar 14, 2007·Journal of Nursing Management·Riitta SuhonenHelena Leino-Kilpi
Feb 26, 2011·Journal of Evidence-based Medicine
Nov 14, 2015·Biological Reviews of the Cambridge Philosophical Society·Matthew Kramer, Enrique Font
Dec 25, 2015·Journal of Anaesthesiology, Clinical Pharmacology·Sukhminder Jit Singh Bajwa
Apr 21, 2012·Journal of Cystic Fibrosis : Official Journal of the European Cystic Fibrosis Society·Judy M BradleyUNKNOWN Allied Health and Nursing Professions Working Group, European Cystic Fibrosis Society
Apr 5, 2013·Western Journal of Nursing Research·Matthew J Hayat
Aug 26, 2006·AACN Advanced Critical Care·Marianne Chulay
Apr 4, 2019·Revista brasileira de enfermagem·Paulo Carlos GarciaFernanda Maria Togeiro Fugulin

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