Assessing Group-Based Changes in High-Performance Sport. Part 2: Effect Sizes and Embracing Uncertainty Through Confidence Intervals

Today's strength and conditioning coach must extend their skill set to include data analysis, understating the validity and utility of p values, effect sizes, confidence intervals, and terms such as the smallest worthwhile change and minimal difference. The aim of part 2 of this 2-part review is to now build on our discussion of null hypothesis significance testing (covered in part 1) and introduce effect sizes, measures of variability, and confidence intervals, culminating in recommendations as to which may be the most viable options within the context of performance-based sport and thus potential methods to report group-based changes. This article has a series of worked examples to aid the reader.