Unfortunately, this won't tell you anything as to how well you can distinguish MP3's from WAV's. If you "accidentally" click the correct one, it may seem as if you have golden ears while all you had was golden luck.
If you want a better (or at least: more statistically correct) answer, then you should participate in an AB/X-test. One such test can be found online here: http://abx.digitalfeed.net
If you're in a hurry, do the short test (5 trials), if you have time and really want to know, take the long test (20 trials). The cool thing about this website is that it also allows you to test AAC, Vorbis and OPUS.