The Mpemba effect is defined as "There exists a set of initial parameters, and a pair of temperatures, such that given two bodies of water identical in these parameters, and differing only in initial uniform temperatures, the hot one will freeze sooner."
So last night I took two cups of water identical in all ways but their temp. One was 95F, one was 41F. I placed them in my freezer which is 0F. The cold cup clearly had the top freeze up first, but I sampled the temperature at the bottom of both cups every 20m. Within 40m both cups were the same temperature. 32.9F. The cold cup still had a bit more ice, but 20m later the cups were indistinguishable in both ice and temp.
I graphed out the temperature change and it turns out the hot water cooled at a rate faster then the cold, especially in the beginning. Of course, water will only go to a little below 32F. But I think I have to call it a tie.
Once I find a test that can be reproduced consistently, I'd love to try ruling out some of the suspected causes. Evaporation, convection, frost, supercooling, solutes, thermal conductivity or the effect of dissolved gasses.
It's kind of intriguing. Especially the rediscovery and the ridicule the student received.
Mpemba asked a visiting physics professor, Dr. Osborne, the same question. This professor replied that he did not know, but he would test the experiment. Dr. Osborne had a lab tech perform Mpemba's test. The lab tech reported that he had duplicated Mpemba's result, "But we'll keep on repeating the experiment until we get the right result."