Thank you, I'll relay this assisted information over to them and get back to you shortly :)

Hi Obadah, Thank you for your patience. The Data Scientist have had a look over this and have confirmed the calculation to be correct: 100 ­* ((2789/7898) - (3016/8644)) / (3016/8644) = 1.207991, rounded to 1.21 We can also see this another way if we just add one decimal to our rounded mean values: ​`3016/8644 = 0.3489`​ ​`2789/7898 = 0.3531`​ ​`100 ­* (0.3531 - 0.3489) / 0.3489 = 1.203`​ So adding one more decimal at least gets us to 1.20, and if we kept going we'd get to 1.207991! Please note, if you were to enable CUPED (which you haven't in this case, but wanted to share information incase you d in future), the exact lift % can sometimes differ from a manual calculation of the difference in means because CUPED does some magic under the hood that changes the means used in estimation (so it could actually be a little different from 0.349 and 0.353. Hope this helps to confirm the calculation for you :)