With one die we can calculate the probability of getting that result and compare it to a distribution of fair dice, that gives us a probability of 0.24% that the average of 100 rolls of a 20 sided fair die is 8.88 or lower.
Knowing op rolled 17 dice (17 sets of 100) we can calculate the probability of that even happening with fair dice to be around 4% meaning very likely that die is unfair.
With one die we can calculate the probability of getting that result and compare it to a distribution of fair dice, that gives us a probability of 0.24% that the average of 100 rolls of a 20 sided fair die is 8.88 or lower.
Knowing op rolled 17 dice (17 sets of 100) we can calculate the probability of that even happening with fair dice to be around 4% meaning very likely that die is unfair.
At least this is how i think this goes