ABSTRACT
This chapter reviews major weaknesses of relying on statistical significance p values, particularly in the case of tests comparing means such as t tests, ANOVAs and correlations. Along with a brief introduction to the notion of statistical power, followed by guides to calculating and using effect sizes and other descriptive statistics including confidence intervals. A related descriptive statistic that is considered and reported even less frequently is the CI. As an alternative, the thorough use of descriptive statistics, including effect sizes and CIs, should replace much of the statistical testing in L2 research. The main reasons for using effect sizes largely correspond to and address the flaws of NHST. However, primary researchers currently do little in the way of using effect sizes to enhance the results or, more importantly, the understanding of the variables and relationships. Both statistical and practical significance are considered and interpreted, and the results of the study are brought together via research synthesis and meta-analysis.
