function mgf( t ) {
		if ( isnan( t ) ) {
			return NaN;
		}
		return exp( (mu * t) + (0.5 * pow( sigma * t, 2.0 )) );
	}
Evaluates the moment-generating function (MGF) for a normal distribution.

@private
@param {number} t - input value
@returns {number} evaluated MGF

@example
var y = mgf( 0.5 );
// returns <number>