Calculating loss when converting from MTS to AVI using FFMPEG
Your paper is asking for an impossible data point unless you have some method of evaluation specified.  By definition, lossy compression results in a loss of data.  Modern lossy compression is very good at discarding data that is not visually meaningful to people, but it is still discarding data.

The amount of data loss when related to a human viewer is thus very subjective and can't be measured.  There are specific methods for comparing the source and output videos for differences and determining loss mathematically, but you need a particular choice of method to apply and you simply apply it.