Premium
Efficiency of split‐mouth designs
Author(s) -
Hujoel P. P.,
Loesche W. J.
Publication year - 1990
Publication title -
journal of clinical periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.456
H-Index - 151
eISSN - 1600-051X
pISSN - 0303-6979
DOI - 10.1111/j.1600-051x.1990.tb01060.x
Subject(s) - periodontal disease , statistics , mathematics , statistical hypothesis testing , stratification (seeds) , medicine , dentistry , biology , seed dormancy , botany , germination , dormancy
The purpose of this paper is (1) to investigate the similarity of the amount, distribution, and, severity of periodontal disease of the within‐patient experimental units, (2) to estimate the relative efficiencies of split‐mouth designs when compared to whole‐mouth designs, and (3) to discuss how stratification on initial pocket depth can result in large differences in the power of the test‐statistics in the different disease categories. Periodontal disease characteristics are not always homogeneously distributed over the within‐patient experimental units and this heterogeneity can reduce the efficiency of split‐mouth designs. In particular, if analyses are stratified on initial pocket depth, sites with an initial probing depth deeper than 6 mm may be small in number and asymmetrically distributed when compared to sites with an initial probing depth less than 6 mm. This may result in large differences of the power of the test statistics among the different disease categories and should lead to a careful interpretation of the statistical significance tests. When disease characteristics are symmetrically distributed over the within‐patient experimental units and a sufficient number of sites is present per experimental unit, the split‐mouth design can provide moderate to large gains in relative efficiency. In the absence of a symmetric disease distribution, wholemouth clinical trials may be preferable.