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Letters

Sample size and study interpretation

Max H. Pittler and Edzard Ernst
CMAJ April 13, 2004 170 (8) 1208; DOI: https://doi.org/10.1503/cmaj.1040153
Max H. Pittler
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Edzard Ernst
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  • © 2004 Canadian Medical Association or its licensors

We welcome the opportunity to restate important limitations of our study, which we discuss in our paper.1 Frank Leung's main concern relates to sample size and its implications. The sample size of 16 for a power of 80% was calculated using an estimated standard deviation of 2.0 and an estimated mean difference of 1.5 cm on a 10-cm visual analogue scale. This mean difference was considered adequate in the expected and confirmed sample of moderately hungover individuals.2 Because of the small sample size and the measurement variation, which proved larger than expected, we discuss in our paper the degree of uncertainty relating to the data and state that this might have obscured a possible true effect. Acknowledging the study's limitations and in the absence of any trend in favour of artichoke extract, we stand by our conclusion that “our findings do not suggest that artichoke extract is effective in preventing alcohol-induced hangover.”

Max H. Pittler Edzard Ernst Complementary Medicine Peninsula Medical School Universities of Exeter and Plymouth Exeter, UK

References

  1. 1.↵
    Pittler MH, White AR, Stevinson C, Ernst E. Effectiveness of artichoke extract in preventing alcohol-induced hangovers: a randomized controlled trial. CMAJ 2003;169(12):1269-73.
    OpenUrlAbstract/FREE Full Text
  2. 2.↵
    Collins SL, Moore RA, McQuay HJ. The visual analogue pain intensity scale: What is moderate pain in millimeters? Pain 1997;72:95-7.
    OpenUrlCrossRefPubMed
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Canadian Medical Association Journal: 170 (8)
CMAJ
Vol. 170, Issue 8
13 Apr 2004
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Sample size and study interpretation
Max H. Pittler, Edzard Ernst
CMAJ Apr 2004, 170 (8) 1208; DOI: 10.1503/cmaj.1040153

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Sample size and study interpretation
Max H. Pittler, Edzard Ernst
CMAJ Apr 2004, 170 (8) 1208; DOI: 10.1503/cmaj.1040153
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