Ordered data are most applicable data in practical surveys. There are two sources of uncertainty in this kind of data which must be considered in any statistical analysis. First is randomness and second is fuzziness. In this paper, the conditional possibility between two consecutive ordered data is considered. Initially, we construct a probability density function such as Bernolli density function for a random variable whose its support is binary ordered data.Then, we produce a M.L estimator for the value of common possibility(conditional possibility)between two consecutive ordered data.