Tuesday, April 21, 2015

R is for . . .

I'm posting Mad-Cool-Math Nuggets for the A to Z Challenge.

Image courtesy: Wikicommons

R is for random data. I got the idea for this blog from 5 Seriously Mind-Boggling Math Facts on the LiveScience website.

Consider all the street addresses in the United States, or the lengths of all the rivers in the world, or stock prices. What will the first digit of these numbers be? A random collection of the nine nonzero digits? Surprisingly not!

For many large collections of numbers, you will see that more of them start with the digit 1 than any other digit--about 30%. The next largest group will start with the digit 2, and so it goes down to 5% of the numbers starting with the digit 9. See the graph above.

You can read more about Benford's Law here. Large sets of numbers that do not follow Benford's law do exist, such as telephone numbers.

Want to try a little test of Benford's law? If you aren't worried about security, put the number of your street address in the comments below. Any street address number will do: home, work, school, favorite bar. I'll start: 249.


  1. Bar graphs were my favorite to do. Line graphs? Not so much.

    I never heard of Benford's law, but that's not surprising.

    Okay...I'll play...306.

  2. That is so interesting. I'm not much of a math geek, but I do like to random facts!

  3. How peculiar! I live at number 7. And before I moved here I lived another number 7, and before that at number 6. That makes 20 or have I lost the plot?!!

  4. I can see how that works out, after all 1 million starts with 1 and you might not get much higher than that, but there'll be a lot of other numbers starting with 9,8,7 below that. I'm probably way off track.

  5. Oh my, that is pretty easy to prove out, and my address adds to that data set: 1809.

    Although, I'm not sure we can actually call addresses a truly random number set because most numeration conventions count up from a specific location, and many streets are short enough to make not make it very far down the numbers.

  6. Mine is the wrecking ball.... starts with 8!

  7. I'm remembering something Adam said on the show Numbers........which I loved! Wish they hadn't taken it off, thought it was a good way to get people interested in math, numbers, realizing how things are tied together. Somehow, I think he said there was no such thing as random......that, even i random there were patterns?

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