A sex researcher called one of his participants 
in a recent survey to check on a discrepancy.

"Sir, in response to the question of frequency 
of intercourse" the researcher said, "you 
answered 'twice weekly.' Your wife, on the other
hand, said 'several times per night.' How could
this be correct?" 

"That's right," the man said, "and that's the way
its going to stay until the house is paid off!"