You can calculate the %, as the % doesn't indicate the fact, but the probability of hit happening, and that would be based on the exemples of the facts that already happened, as the % for it not happening would cover the other variables, that if they got a lower %, they would be so important as the one we're discussing.
Wrong. Wrong. Absolutely wrong.
The main flaw in this isn't that you can't calculate it mathematically... in fact, you can make ANYTHING that exists be represented in the form of a mathematical model.
The more important question to ask is: How ACCURATE is that model?
And, sir, the reason why I said "Wrong" is because your mathematical model may be precise, but not accurate.
Two different things. Yes, you may very well be able to calculate the % of children who become gay (if you believe it is a choice firstly) if they have homosexual parents as opposed to heterosexual parents and be precise with that data, however, is it accurate?
Is it close enough to the REAL WORLD SCENARIOS that actually happen? And the answer, to that... is NO.
There are way too many variables to be able to accurately (not precisely) make a statement that says:
"A child has a higher chance of being gay if they have homosexual parents than heterosexual parents"
The only way this would work is if you segregated each set of parents from one another, as well as from society and still somehow was able to allow the parents to raise their children in what is seen as "NORMAL" by society.
Which in and of itself is impossible.
The reason is children are bombarded with media, other social beings, animals, education, history, culture... you name it... any one of these can influence any one child into becoming gay using your logic. You would have to segregate that child from all of these and basically, the child could only speak to, eat with, go out with, see, hear, smell, touch and live with their parents ONLY.
Which would be impossible.