These three files are of the same 57-second piece of music. One was ripped to FLAC, one was ripped to a 75%-quality WMA and one was ripped to a 10%-quality WMA:
When you look at the original file sizes involved, the FLAC is 3MB, the 75% WMA is 510KB and the 10% WMA is just 200KB.
However, I’ve now converted all three files back to [uncompressed] WAV, so that -give or take a dozen bytes or so- all file sizes are pretty much identical (9MB or thereabouts). You won’t be able to tell which is which just by comparing file size, in other words, but each has been encoded at wildly different quality levels.
So the question is, can you tell which file is which, just by listening (checking the wave form in something like Audacity is not allowed!)?