Here is a brief explanation on the law of small numbers. The Law of Small Numbers infers that when people see two small numbers that they have the natural propensity to round the numbers down to equal the same. This is a error in that small numbers may make a difference. In such a case as the story with the patient, it would be incorrect to round 4% down to 0% because they are relatively close. 4% may be significant in a diagnosis. Law of Small Numbers may make people act in irrational ways.


Examples may include: first people buying lottery tickets. Although a probability exists though minute, the probability by most people are thought to be zero because of the general rounding. When a large group of people neglect to show up except for a few, it is not uncommon to hear the leader say ‘nobody is here’ inferring rounding close to zero relative to the sum. People look at speeding tickets and think about how many cars on the road in total. As a consequence because there are so many cars the driver may think they are immune to tickets effectively mentally reducing the probability to zero when in fact a probability exists.