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Table 2 Equations to calculate MD, SD, and correlation coefficient

From: Comparative efficacy of statins, metformin, spironolactone and combined oral contraceptives in reducing testosterone levels in women with polycystic ovary syndrome: a network meta-analysis of randomized clinical trials

Equation 1:Mean Change (MD) = M2 − M1
Equation 2:\( SD\ Change=\sqrt{SD{1}^2+ SD{2}^2-\left(2\times Corr\times SD1\times SD2\right)} \)
Equation 3:\( Corr=\frac{\left( SD{1}^2+ SD{2}^2- SD\ {change}^2\right)}{\left(2\times SD1\times SD2\right)} \)
  1. M1: Mean level of testosterone at baseline; M2: Mean level of testosterone after treatment, SD1: Standard deviation of testosterone level at baseline; SD2: standard deviation of testosterone level after treatment; Corr: correlation coefficient, which is the value that describes how similar the baseline and final measurements were across participant [14]
  2. Equation 1 was used to calculate the mean difference of testosterone between baseline and after treatment, Equation 2 was used to impute a standard deviation of the change from baseline, and Equation 3: was used to calculate the correlation coefficient [14]. Corr was calculated using the SD1, SD2, and SD Change; since the SD change was not reported by some of the included studies, it was extrapolated from other similar studies [5, 8]