A probability is a measure of how likely it is that something will happen and although just guesses, they are very careful guesses. By comparing the weather conditions today with the weather conditions from past days forecasters try to predict what's going to happen tomorrow, however, sometimes the forecast isn't correct, because no matter how much information is available a probability is still a guess.

Title from cassette insert. Video # 401-31-896. Originally an episode of the television program Bill Nye, the science guy.