ABSTRACT
INTRODUCTION So far, information from a single sample has been used to make deductions about a population mean using a 95% confi dence interval and a hypothesis test. However, often in dentistry two different groups need to be compared on an outcome. For example:
➤ Do amalgam fi llings stay in place longer than composite fi llings? ➤ For privately treated patients, is the mean cost of a crown the
same for men and women? ➤ Is the consultation length (in minutes) of a routine check-up the
same for adults with a dental insurance plan as for those without dental insurance?
