Before revision:  Under appropriate restrictions, we show that the conditional distribution of the stochastic inefficiency term  is a folded normal distribution . The latter reduces to the half-normal distribution when both inputs and environmental variables are independent of the stochastic inefficiency term.
After revision:  Under appropriate restrictions, we show that the conditional distribution of the stochastic inefficiency term is a folded normal distribution , which reduces to the half-normal distribution when both inputs and environmental variables are independent of the stochastic inefficiency term.