I wrote my undergraduate thesis on why witches were women, but back in the 1990s so I don’t recall much if the literature (which would be massively out of date anyway now) but it’s a very interesting topic, and very much linked to female power and productivity.
I seriously hope you didn't pass, as that is incorrect, and as alltoomuchrightnow as pointed out, the word witch or ( more accurately) it's original spelling of wicche, is gender neutral. It is only in modern times that witches have been sort of "hollywoodised" into the type of witch we see in modern literature, and indeed Christian literature has played it's part in portraying them as we see them today.
The persecution of Witches, both male and female, was (generally speaking) not from within their own communities, where they were valued for their skills, healing and general knowledge and wisdom, but from the religious establishment, where they were viewed as heretics, and (quite incorrectly, of course) accused of "devil worship" or "Satanism". This misconception is still as strong today, where paganism, in many peoples eyes, is still associated with these things by ignorant people (and film makers!).
Of course, the medieval religious establishment was an incredibly misogynistic hierarchy, and the persecution of witches was also related to the power struggles between the Protestant and Catholic Church in the turbulent times from the mid 1500's to the late 1600's.
The "Witch-hunts" of these times were more the Church wielding it's power over the masses, than an active attempt to wipe out pagan beliefs/religions.
Also in these times, an older wiser widowed or single woman, whilst still being a rarity, would not be as rare as an older wiser man, who's chances of surviving the many wars greatly diminished the older they got, and, if found to be a "wicche" would more likely be found more useful to be pressed into slavery, than executed.
Probably the most famous "Witch Hunt" of modern times is the Salam Witchcraft trials of the 1690's, where 20 people were executed, of which 15 were women. If this is taken as an example of the ratios involved, then of the estimated 40,000 executions over this 100 year odd period, then at least 75% of them would have been women.
Disclaimer: I'm not a Witch, but have a deep interest in (mainly) English folklore/paganism.