This isn’t a trick question. The answer is simply to perform a hypothesis test:
The null hypothesis is that the coin is not biased and the probability of flipping heads should equal 50% (p=0.5). The alternative hypothesis is that the coin is biased and p != 0.5.
Flip the coin 500 times.
Calculate Z-score (if the sample is less than 30, you would calculate the t-statistics).
Compare against alpha (two-tailed test so 0.05/2 = 0.025).
If p-value > alpha, the null is not rejected and the coin is not biased.
If p-value < alpha, the null is rejected and the coin is biased.
