The “Law” of Big Numbers…In Action!!!

Driving home the other day, in my newly purchased Jeep, I notice a cop car in my rear view mirror.  As is the typical automatic response, I glanced down at my speedometer and noted that I was a full 5 km below the speed limit.  Reassured in the fact that I had no reason to be pulled over for speeding, I continued on my journey home.

However, after several blocks, I noted that the cop car seemed to be following me.  “Probably nothing”, I thought to myself.  “Most likely just a coincidence” I thought.  The police officers must be headed in the same direction as me, “nothing to worry about”.

Moments later I see the light bar on the top of the patrol car light up.  I check in my rear view mirror and notice that the police officer indicating that he wants me to pull over.  Being the outstanding citizen that I am, I do.

Once pulled over the police officer informs me that my licence plate is registered to another vehicle, a red ford ranger.  I inform the officer, that within the last 2 days, I sold that vehicle (the red ford ranger), and that I transferred the plates from that vehicle to my new Jeep.  I then hand the police officer all of the appropriate paperwork/registration documents to prove this.  The officer looks over the documents and then laughs, “Yeah everything is in order.  Sometimes it takes the powers that be a few days to update the system, and so we do not get the updated information in our system for a few days.  Sorry about pulling you over.  Have a good day”

As the police officer is about leave I stop him and inquire if I could ask him a quick question. 

“Sure” the officer says, “what is it?”

“I know you guys run a plate when you pull someone over, but I had not been doing anything wrong, my vehicle is in good working order, and I was not speeding, so as far as I can tell you had no reason to pull me over.  So when did you run my plate?” 

The officer lets out a little chuckle.  “There are typically 2 of us in the squad car.  So the person in the passenger seat is not busy he runs plates, at stop signs, red lights, and even as we are driving.  We pass by a couple thousand vehicles per shift, and we run as many licence plates as we can”.  The officer then goes on to inform me that this is actually a rather effective manner in catching people with outstanding warrants.  “Everything from unpaid speeding tickets to assault and robbery”. 

The police officer finishes by telling me, “It is the law of big numbers.  If you go through enough plates you are bound to find something!  Have a nice day”

So even if catching a criminal by randomly running his/her licence plate is a 1 in a 1,000,000 event (and by this police officer’s account it happens a lot more regularly then that)…

That means that it will still happen at least once!  And if the same set of circumstances are repeated 10 million or 100 million times, then a one in a million event, actually becomes rather common.

This has been the skeptical samurai

Working to serve…

Through the process of inquiry…


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