Friendship Between Women:
A women didn't come home one night. The next day she told her husband that she had slept over at a friend's house. The suspicious 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 suspicious woman called her husband's 10 best friends.
Eight of them confirmed that he had slept over, and two claimed that he was still there.