Quantiles are values taken at regular intervals from the inverse of the cumulative distribution function (CDF) of a random variable. Dividing ordered data into essentially equal-sized data subsets is the motivation for -quantiles; the quantiles are the data values marking the boundaries between consecutive subsets. Put another way, a -quantile for a random variable is a value such that the probability that the random variable will be less than is at most and the probability that the random variable will be greater than is at most . There are of the -quantiles, one for each integer satisfying . In some cases the value of a quantile may not be uniquely determined, as can be the case for the median of a uniform probability distribution on a set of even size.