What is a good sample size for determining whether dice are truly random?
All real dice are biased, incidentally. The very best dice manufactured would take many thousands of rolls for statistical methods to reveal that bias with a fair degree of certainty. The stronger the bias is, the easier it is to see it and the less rolls (i.e., lower statistical “power”) is required to demonstrate the bias. Interestingly, in statistics, a die can never be proven biased. You can only make a statement phrased like the following: The chance of observing the obtained data set with 1000 rolls, if the die were truly unbiased, is 0.01%. (In other words, if you did 10,000 “thousand-roll” trials, only 1 of them would be expected to produce such extremely biased results as were observed.) The more you roll the die, the smaller that percentage figure gets. The more heavily the die is biased, the fewer the rolls necessary to get to any given degree of certainty.
