LEARNING Describe the advantages of a two-group design compared to an experiment with more than two groups.
Comparing Means for More Than Two Groups
As noted in the previous section, research questions often require more than two groups to evaluate the functional relation between an independent and a dependent variable, or to include several different control groups in a single study. In these cases, a single-factor multiple-group design may be used. For example, a researcher may want to compare driving performance under three telephone conditions: while talking on a cell phone, while texting on a cell phone, and without using a phone. Another researcher may want to examine five different dosages of participants, and a single-factor analysis of variance (ANOVA) (independent measures) is used to determine whether there are any significant differences among the means (see Chapter 14). When the ANOVA concludes that significant differences exist, some form of post hoc test or posttest is determine exactly which groups are significantly different from each other.