ABSTRACT
Although the topics of this chapter are generally not considered to be examples of effect sizes, and they might not be expected by some readers to be found in a book on effect sizes, this section and chapter 3 demonstrate that there are connections between confidence intervals and effect sizes, both of which can provide useful perspectives on the data. The confidence intervals that are discussed in this chapter and the effect sizes in chapter 3 all provide information that relates to the amount of difference between two populations’ averages, including means. When the dependent variable is a commonly understood variable that is scaled in familiar units, such as weight in research that compares two weight-reduction programs, a confidence interval and an effect size can provide useful and complementary information about the results. Note that some authors do consider confidence intervals to be estimates of effect size (Fidler, Thomason, Cumming, Finch, & Leeman, 2004).
