![]() Guidance on sample size (Central Office for Research Ethics Committees, 2007: 23) requires that 'the number should be sufficient to achieve worthwhile results, but should not be so high as to involve unnecessary recruitment and burdens for participants'. The UKECA recognise various committees throughout the UK that can approve proposals for research in NHS facilities (National Patient Safety Agency, 2007), and the scope of research for which approval must be sought is defined by the National Research Ethics Service, which has superceded COREC. ![]() The era of self-regulation in UK research ethics has ended (Kerrison and Pollock, 2005). Since the introduction of a new UK Ethics Committee Authority (UKECA) in 2004 and the setting up of the Central Office for Research Ethics Committees (COREC), research proposals have come under greater scrutiny than ever before. Key words: Power, sample size, beta level, effect size, research ethics committees, GPower GPower may be used to replicate the examples in this paper, which may be generalised to more complex study designs. Alpha and power levels can be pre-specified, but effect size is more problematic. Researchers and research ethics committee members need to be familiar with the technicalities of Sample size estimation in order to make informed judgements on sample size, power of tests and associated ethical issues. The examples illustrate the importance of effect and sample size in optimising the probability of a study to detect treatment effects, without requiring these effects to be massive.Ĭonclusions. Examples involving t-tests, analysis of variance (ANOVA) and chi-square tests are used. GPOWER TO CALCULATE EFFECT SIZE SOFTWAREBasic concepts are examined before utilising the statistical software package GPower to illustrate the use of alpha level, beta level and effect size in sample size calculation. To enable researchers and research ethics committee members with non-statistical backgrounds to use freely available statistical software to explore and address issues relating to sample size, effect size and power. ![]() Sample size estimation is now a major, but often misunderstood concern for researchers, academic supervisors and members of research ethics committees.Īim. The issue of sample size has become a dominant concern for UK research ethics committees since their reform in 2004. ![]()
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