MathPHP\Probability\Distribution\Continuous\Exponential::mean PHP Method

μ = λ⁻¹

public static mean ( float $λ ) : number
$λ	float	often called the rate parameter
return	number

    public static function mean(float $λ)
    {
        Support::checkLimits(self::LIMITS, ['λ' => $λ]);
        return 1 / $λ;
    }

Exponential