May I suggest that you run some trials where the owner begins his journey home and then cancels it in favor of more errands. Also some where he thinks about starting home but doesn't. I guess at least two hours should go by before he really comes home.
Also, are these double blind? Someone who is neither the owner nor the principal investigator should randomly choose the time to head home and call the owner.
And, of course, all telephones in the house should be turned off. Yes, I know I'm assuming dishonesty. Sorry.
~~ Paul |