function cdf( x ) {
		if ( isnan( x ) ) {
			return NaN;
		}
		if ( x < beta ) {
			return 0.0;
		}
		return 1.0 - pow( beta / x, alpha );
	}
Evaluates the cumulative distribution function (CDF) for a Pareto (Type I) distribution.

@private
@param {number} x - input value
@returns {Probability} evaluated CDF