In reply:  Determining the sample size in a clinical trial

Kirby, Adrienne; Gebski, Val; Keech, Anthony C

doi:10.5694/j.1326-5377.2003.tb05241.x

Topics

Statistics, epidemiology and research design

In reply: A key message of our article is that the minimum possible difference that would render the intervention clinically worthwhile needs to be determined in the design phase of the study.1 This potential clinical difference (net advantage over standard care) must, of necessity, incorporate the potential trade-offs between any outcome advantages and associated toxicities and/or cost disadvantages.

Correspondence:

1. Kirby A, Gebski V, Keech AC. Determining the sample size in a clinical trial. Med J Aust 2002; 177: 256-257. <eMJA full text>
2. Shakespeare TP, Gebski VJ, Veness MJ, Simes J. Improving the interpretation of clinical studies using confidence levels, clinical significance curves and riskbenefit contours. Lancet 2001; 357: 1349-1353.
3. Frieman 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 randomised control trial: survey of 71 "negative" trials. N Engl J Med 1978; 299: 690-694.
4. Lau J, Schmid CH, Chalmers TC. Cumulative meta-analysis of clinical trials builds evidence for exemplary medical care. J Clin Epidemiol 1995; 48: 45-57.

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