The possibility of continuous uniform distribution is an uninterrupted arrangement , which has the same probability of any interval of the same length . If an evenly arranged random variable only takes a value between a to b , where a <b, then the probability density function of the evenly arranged will be: Sometimes 1 / (b - a), in some cases 1 / (2 (b - a)) . Because of these two marginal values f (x) dx or xf (x) dx integration does not mean any change, f (a) and f (b) are usually unimportant .