
 Prior probability  Wikipedia, the free encyclopedia 
  We could specify, say, a normal distribution as the prior for his speed, but alternatively we could specify a normal prior for the time he takes to complete 100 metres, which is proportional to the reciprocal of the first prior. 
  An example is a prior distribution for the temperature at noon tomorrow. 
  statistical inference, a prior probability distribution, often called simply the prior, of an uncertain quantity p (for example, suppose p is the proportion of voters who will vote for John Kerry) is the probability distribution that would express one's uncertainty about p before the "data" (for example, an opinion poll) are taken into account. 
 en.wikipedia.org /wiki/Prior_probability (916 words) 
