Data is not biased. Interpretation can be certainly.
If for instance it’s found that Tierney calls twice as many fouls against us as opposed to any other team, the data bears that we are penalized twice as much. Now the why could be debated unless there’s more data found to show he’s making biased judgements.
It would be hard to ever prove bias, but there certainly is compelling evidence to support that hypothesis.
You are right, Data in and of itself doesn't have bias....but how, and by whom, that data is compiled is subject to bias (the main reason a court of law relies on independent experts)..... ALL human decision making is subject to bias...again this is why courts rely on two independent fingerprint experts, neither of which can know the others opinion, they both have to arrive at the same decision, independent of each other.
Your Tierney point has merit...but that's a big if....and then of course you would have to include whether other referee's call more fouls against us, if that held true you'd have to conclude we probably commit more fouls.
Examining data is a pretty complex matter.