Journal of Dental Research, Vol 70, 118-122, Copyright © 1991 by International & American Associations for Dental Research Online Journals
Power and sample size calculations for clinical trials of myofascial pain of jaw muscles
T. T. Dao, G. J. Lavigne, J. S. Feine, R. Tanguay and J. P. Lund
Faculte de medecine dentaire, Universite de Montreal, Canada.
When a clinical trial is planned, the approximate number of subjects needed
for significant differences between/among groups to be detected must be
estimated. Sample-size calculations provide the investigator with this
information. This paper discusses the choice of outcome measures and
describes the steps used to estimate the numbers of subjects necessary for
a study that compares treatments for patients with chronic myofascial pain
of jaw muscles. Within- and between-subject variances were estimated for
the chosen variables, the subjects' pain ratings on visual analogue scales.
Sample sizes were then calculated for theoretical differences between
groups by pre-treatment means and overall standard deviations (Cohen,
1977). The results of this analysis can be used by other researchers when
planning studies involving these types of patients.
