def normalize_correlation(coincidence_count, coachfile_count):
    """Calculate a correlation between 0 and 1 for scoring.

    Essentially, we are calculating:

        P(Y|X) = times_XY_committed_together/times_X_committed

    Example:

    >>> normalize_correlation(3, 6)
    0.5
    """
    return 1.0 * coincidence_count / coachfile_count
