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Inadequacy of sample sizes in clinical trials of laboratory parameters attributable to invalid statistical assumptions
Author(s) -
Halpern Elkan F
Publication year - 1994
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1994.158
Subject(s) - sample size determination , statistics , clinical trial , econometrics , sample (material) , medicine , mathematics , chemistry , chromatography
Clinical trials often determine the sample size based on the use of statistical methods such as analysis of variance, t tests, and rank sum tests, which compare mean or median values. The resulting studies rarely are big enough to show that the method is based on mistaken assumptions. Data from a recent clinical trial of nephrotoxicity associated with the use of contrast agents during angiography found a significant difference on the order of the difference that previous studies had intended to detect. It also showed that a central assumption does not apply to changes in serum creatinine. As a result, the previous studies had considerably lower power than believed. Their lack of significance reflected only the mistaken assumption. Analysis of variance, t tests, and rank sum tests may be just as invalid for other clinical parameters. Lack of significance cannot be automatically taken to imply a small treatment effect. Clinical Pharmacology and Therapeutics (1994) 56, 437–444; doi: 10.1038/clpt.1994.158