text: how does the cable network determine how many people are watcing certian shows?   the leader in this space is nielson media research - you'll find all the answers on their site including how they measure their audience, how they sign people up (random sample), etc.  http://www.nielsenmedia.com/nc/portal/site/public/menuitem.3437240b94cacebc3a81e810d8a062a0/?vgnextoid=130547f8b5264010vgnvcm100000880a260arcrd