Benford’s Law

I read up on Benford’s Law recently, which explains one of the many things that I have always wondered about. You see, my apartment number is 15029, and a lot of the apartments in my complex have a number starting with a 1, and so it is with a friend’s apartment complex I had been to the day before.

Also known as the first-digit law, it says that a number in things such as the front page of the Times, or on tax return forms have a 30-odd percent probability of starting with the numeral 1. In other words, if you look at real-life source of numerical data, the probability for different numerals being the first in the numbers is not the same.

This article also opens with a compelling classroom exercise in probability. The professor asks the students to toss a coin 200 times and write down the sequence of heads and tails observed. He often identifies fakers, who just write down a seemingly random sequence (in stead of actually tossing the coin 200 times), with surprising accuracy. The key is the fact that in 200 coin-tosses, the chances of 6 consecutive heads or tails appearing is surprisingly high, but not many fakers would think this would be so, and would avoid writing sequences with 6 consecutive heads or tails!

Interesting stuff – good examples of “laws” or truths of daily life that are just sitting out there, waiting to be written down as a “law”. Hope I stumble across some, sometime. Carthik’s Law – that would be the day, hell yeah!

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2 Responses to Benford’s Law

  1. Yuvi says:

    Booh that’s way too tough. Our Maths teacher doesn’t even write down all the probabilities for throw of a die twice:D

    Got here through Sabarish’s Blog, and WOW.

  2. Mike says:

    There is free software, including charts, for doing data analysis to test conformity with Benford’s law. Details are at