COMMENTS ON A COMMENTARY - STATISTICAL EVALUATION OF SPLIT MOUTH CARIES TRIALS

When results of split mouth caries trials are reported, the most frequ ently used outcome measures are ''effectiveness'' and ''net gain''. In a recent review by Riordan & FitzGerald (Community Dent Oral Epidemio l 1994;22:1927) of the statistical analysis of data from such trials, the close connection between effectiveness and the traditional epidemi ological outcome measure, relative risk, was pointed out and the latte r measure Mras recommended. The confidence intervals for these paramet ers were, however incorrect. This note provides valid confidence inter vals for net gain, effectiveness and relative risk based on data from split mouth trials and presents examples oi the calculations.