Regarding Eqs. (11) and (13), we can conclude that standard deviation of lead-time demand for each product does not have any influence on the bullwhip effect. Now we continue our research to determine two relationships for VarðdÞ and VarðqtÞ as numerator and denominator of bullwhip ratio. As mentioned before, Eq. (2) can be used as the variance of market demand and to determine variance of orders, we follow our calculations based on Eq. (13) in the next section.