<qa>  What is the Pearson Product Moment correlation coefficient?As stated above, our measure of effect size will be the Pearson Product Moment correlation coefficient r. For this study we chose an effect size of r .50 as the smallest effect size that would be clinically meaningful, and then calculated that we would need a sample size of 26, to obtain power of 81, and a 95.0 confidence interval r .13 to r .75 that would not include zero. Rosenthal, 1991. 