According to Badawy et al. (2009), the reported differences between the two protocols as regards the total number of follicles, the number of follicles > 14 mm in diameter, the number of follicles > 18 mm in diameter, and endometrial thickness are translated into huge effect sizes (Cohen's d) of d = 6.3, d = 6.4, d = 3.2, and d = 1.98, respectively. The effect size (d) is calculated as follows: d= ((x1-x2))/sp, where (x1 - x2) is the difference between the means of the two protocols and sp is the pooled standard deviation.