Woody Allen once said "Being bisexual doubles your chance of a date on Saturday night."
But that's obviously/logically false! What should he have said?
(In reply to It's not as funny, but ... (spoiler)
by Steve Herman)
Assuming the probability of getting a date is D (independently of sex and sexual orientation), bisexuals have 1-(1-D)² probability of getting a date, which works out to 2D-D², so instead of doubling, it goes up by (2-D).
As to the illogical part: if D>50%, Allen's probability of getting a date would be over 100%!