How do tv stations do this?

Question

How do they determine the ratings? Do you have to watch an entire show for it to count or just change the channel to it for a couple of seconds?

Answer 1

There are different ways to determine rating, but the most common one today is to install a special box into the homes of selected people. This box monitors all of their TV usage (what they watch, how long, channel srufing, etc) and reports it to the rating companies. It is then up to company to decide what they count as a "watch". Usually anything under 10-15 seconds is ignored as channel surfing. (Although some stations like to know that people went by without stopping so they can try to figure how why you did not stop).

Anything longer then that becomes important, because it means you watched a little bit and then didn't stay. Apparently you did not like what you saw - a negative vote for the program. So it is important to track when something less than a whole show is watched.