People use television in different ways and for different reasons. The variable use of television makes audience measurement challenging. The principles of measurement dictate that subjects which have a particular property should be included in a count, and those that do not, excluded. Additionally, the rules that govern inclusion and exclusion should be free of ambiguity. At present, U.S. television audience measurement is based on the concept of "watching." "Watching" is a subjective term that, when applied in a real-world setting, is open to many different interpretations by those who measure, those who are measured, and those who use the information obtained from the measure. Thus, the system allows that two people who are doing the same thing may not be counted as equal. It will also allow the reverse -- that two people who are doing different things may be counted as equal. The ambiguity inherent in the current system led to an investigation of a simpler, more objective definition of the television audience -- "in-the-room with the TV set on." Nearly all of the people who are in the room with a tuned television set are involved with television or have the potential to be involved with television. The "in-the-room" audience definition provides something that is currently lacking in television audience measurement: a consistent, first-level measure of potential audience.