Answer
Yes, the dice are loaded.
Work Step by Step
The sample space for "rolling a die" is: S = {1, 2, 3, 4, 5, 6}. So, $N(S)=6$. For the event "rolling a six" we have one outcome:
E = "rolling a six" = (6). So, $N(E)=1$.
Using the Classical Method:
$P(rolling a six)=\frac{N(E)}{N(S)}=\frac{1}{6}\approx0.167$
So, you after rolling a fair die 400 times, we would expect to roll a six $0.167\times400=66.8\approx67$ times. We would, also, expect the same frquency for each value of die.
We conclude that the dice are loaded.
