This sample size provides 90% power to detect an average increase of one additional endometriosis lesion with the NBI examination (white light/NBI group) compared to white light only examination (white light/white light group). To note, this power calculation was based on data from the pilot study that showed an average of 2 lesions (per patient) found using white light and 3 lesions (per patient) detected using NBI; the calculation assumes a common standard deviation of 1.