Numbers without proof

 How meaningful, if at all, are all these guesses made about how much sleep people get? When I wake up in the middle of the night, I can look at my watch and know what time it is. But I have no idea when I dropped off to sleep.
    If the sleepers on whom the claims are based are not wearing a gadget monitoring their sleep time, and this info is not included in the report, anything the sleepologists claim is worthless.