Of a sample of 20 people, 10 participants self-reported experiencing goosebumps when listening to music, 10 didn't; the DTI brain machine finds they have different connectivity between certain regions of the brain.

Who gets to be _the special_ out of two sets with an equal number of members? :)

I suspect the sample was chosen to get two equal sets, as for an experiment like this you want to maximise the data from the two groups, as you are not trying to measure the incidence of the effect but rather the differences from the effect.