Investigation:

You are in the planetqhe casino betting on a game of Biases. Here is how the game works;

The casino has a device that manufactures coins. Sometimes the coin is fair, at other times it is not. All the gamblers are made aware of this fact in the house rules. Part of the attraction of the game is to figure out the bias and exploit it! The dealer has 2 coins; one black and one red. The dealer throws each coin 5 times and adds up the number of heads. Gamblers at the table can place bets on any amount of heads for each coin.

You watch the gamblers play. On one day you notice that the number of times that the red coin comes up with 4 heads is pretty much the same amount of times that the black coin comes up with 4 heads. You also figure that, on this day, the coin is fair. On another day, you note that, again, the number of occasions that 4 heads come up is approximately the same for each coin - but you also notice that one of the coins is very biased.

How is this possible?