Friendship among Women:
A woman doesn't come home one night. The next day she tells her husband she slept over at a friend's house. The man calls his wife's 10 best friends. None of them know anything about it.

Friendship among Men:
A man doesn't come home one night. The next day he tells his wife he slept over at a friend's house. The woman calls her husband's 10 best friends. 8 of them say he did sleep over and 2 claim he's still there