SAMPLE SIZE DETERMINATION IN HEALTH RESEARCH
AbstractOne of frequently asked question by medical and dental students / researchers is how to determine the sample size. Sample size calculations is necessary for approval of research projects, clearance from ethical committees, approval of grant from funding bodies, publication requirement for journals and most important of all justify the authenticity of study results. Determining the sample size for a study is a crucial component. The goal is to include sufficient numbers of subjects so that statistically significant results can be detected. Using too few subjects’ will result in wasted time, effort, money, animal lives etc. and may yield statistically inconclusive results. There are numerous situations in which sample size is determined that varies from study to study. This article will focus on the sample size determination for hypothesis testing that involves means, one sample t test, two independent sample t test, paired sample and one-way analysis of variance.Keywords: Sample size; hypothesis testing; one sample t test; two independent sample tests; paired sample t test; one-way analysis of variance
Daniel WW. Biostatistics: a foundation for analysis in the health sciences 7th ed. New York NY: Wiley, 1999; p.180–5, 268–7.
Pagano M, Gauvreau K. Principles of biostatistics. Pacific Grove, Calif: Duxbury, 2000; p.246–9, 330–1.
Altman DG. Practical statistics for medical research. London, England: Chapman & Hall; 1991.
Freiman JA, Chalmers TC, Smith H Jr, Kuebler RR. The importance of beta, the type II error and sample size in the design and interpretation of the randomized control trial. N Engl J Med 1978;299(13):690–4.
Rosner B. Fundamentals of biostatistics 5th ed. Pacific Grove, Calif: Duxbury, 2000; p.308.
Feinstein AR. Principles of medical statistics. Boca Raton, Fla: CRC, 2002; p.503.
Snedecor GW, Cochran WG. Statistical methods 8th ed. Ames, Iowa: Iowa State University Press, 1989; p.52, 439.
SPSS. Sample Power. [internet]. [cited 2012 March 3]. Available from: www.spss.com/SPSSBI/SamplePower/
Frison L, Pocock S. Repeated measurements in clinical trials: analysis using mean summary statistics and its implications for design. Stat Med 1992;11(13):1685–1704.
Fleiss JL. Statistical methods for rates and proportions 2nd ed. New York, NY: Wiley, 1981; p.45.
Hoenig JM, Heisey DM. The abuse of power: the pervasive fallacy of power calculations for data analysis. Am Stat 2001;55:19–24.
Kirkpatric LA, Feeney BC. A Simple Guide to SPSS for Windows: Versions 8, 9, and 10. 4th ed. Wadsworth; 2000.
Roberts I, Kwan I, Evans P, Haig S. Does animal experimentation inform human healthcare? Observations from a systematic review of international animal experiments on fluid resuscitation. Br Med J 2002;324(7335):474–6.
Thornley B, Adams C. Content and Quality of 2000 Controlled Trials in Schizophrenia over 50 Years. BMJ 1998;317(7167):1181–4.
Wheeler RE. Portable Power. Technometrics 2001;16:193–201.
Wright T. A simple algorithm for tighter exact upper confidence bounds with rare attributes in finite universes. Stat Probab Lett 1999;36(1):59–67.
Lipsey MW. Design Sensitivity: Statistical Power for Experimental Research. Newbury Park, Calif: Sage Publications, 1990; p.207.
Mace AE. Sample-Size Determination, New York: Reinhold; 1964.
Muller KE, Benignus VA. Increasing Scientific Power with Statistical Power. Neurotoxicol Teratol 1992;14(3):211–9.
Gerstman BB. Basic Biostatistics: Statistics for public health practice. Boston: Jones & Bartlett Publishers; 2008.
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