A television pilot is a test episoe of an intended television series. It is an early step in the development of a television series, much like pilot lights or pilot studies serve as precursors to start of larger activity. Networks use pilots to discover whether an entertaining concept can be successfully realized. After seeing this sample of the proposed product, networks will then determine whether the expense of additional episodes is justified. They are best thought of as prototypes of the show that is to follow, because elements often change from pilot to series. Variety estimates that only a little over a quarter of all pilots made for American television succeed to the series stage, although the figure may be even lower.