thermodynamics - Effusion of Ideal Gas

I just calculated that for an ideal gas inside a container, the average kinetic energy for molecules that are striking the walls of the container is larger than the average kinetic energy of the molecules comprising the entire gas. Specifically, my result was $$\frac{E_{walls}}{E} = \frac{4}{3}$$ where $E=\frac{3}{2}T$. I am pretty sure that this is correct. My question is then if I have a container of gas in vacuum and I poke a hole in it, let some gas escape, and then close the hole before all of it escapes, am I right in thinking that due to my result above, the molecules that escape are more likely to have higher energy than the average energy of the whole gas, and as a result the energy and temperature of my system will have decreased?