cdf
Returns the cumulative distribution function (CDF) value at x.
The CDF gives the probability that a random variable drawn from this distribution is less than or equal to x. Equivalently, it is the area under the probability density curve from negative infinity up to x.
Return
the probability that a value is less than or equal to x, in the range [0, 1].
Parameters
x
the point at which to evaluate the cumulative probability.