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Statistics Toxicology
Volume 180 - Issue 8

Parallel infusion of hydrocortisone ± chlorpheniramine bolus injection to prevent acute adverse reactions to antivenom for snakebites

Author:  Val J Gebski

Med J Aust 2004; 180 (8): 428-429. || doi: 10.5694/j.1326-5377.2004.tb06005.x
Published online: 19 April 2004
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Val J Gebski

Principal Research Fellow, NHMRC Clinical Trials Centre, Level 5, Building MO5, Mallett Street Campus, University of Sydney, NSW 2006. valATctc.usyd.edu.au

Comment: Kularatne and Gawarammana compared the proportion of side-effects given in their table above using the well-known (and easily understood) test of the difference between two proportions using the normal distribution. However, as each of these proportions follows a binomial distribution (13 “successes” out of 16 trials and 11 “successes” out of 21 trials), the normal approximation is only useful if the number of trials is greater than 30.

Because of the small sample sizes, “exact” methods better reflect the true difference (in terms of P values and confidence intervals) between the two proportions. The more complicated methods (different formulations of the exact test) and the resulting confidence intervals provide a clearer indication of whether the proportions are indeed different (statistically). In this instance, the evidence is not sufficient to declare the two proportions statistically different.

Author

  • Val J Gebski1
  • 1. NHMRC Clinical Trials Centre, Level 5, Building MO5, Mallett Street Campus, University of Sydney, NSW 2006.

Correspondence: val@ctc.usyd.edu.au

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