# Base Rate Fallacy

A base rate fallacy is committed when a person judges that an outcome will occur without considering prior knowledge of the probability that it will occur. They focus on other information that isn't relevant instead. Imagine that I show you a bag of 250 M&Ms with equal numbers of 5 different colors. Then, I ask you what the probability is I will pick a green one while my eyes are closed? I also tell you that green M&Ms are my favorite and yesterday I picked out twice as many green M&Ms than red ones. If you ignored the fact that there are 50 of each color, and instead focused on the fact that I picked out twice as many green M&Ms than red yesterday, you have commited a base rate fallacy because what I did yesterday is irrelevant information.