Friendship Between Women:

A woman didn't come home one night. The next day she told her husband that she had slept over at a friend's house. The husband called his wife's 10 best friends. None of them knew about it.

Friendship Between Men:

A man didn't come home one night. The next day he told his wife that he had slept over at a friend's house.
The wife called her husband's 10 best friends. Eight of them confirmed that he had slept over, and two claimed that he was still there.