## Saturday, March 29, 2008

### More 11:11 mystical nuttery

Out of the blue I received an email about my post the other day about Benford's Law and 11:11:
every time i look at the clock the number add up to 11. how does that get explained

OK. Well, it turns out that that's pretty simple to explain: the sum 11 is the most common sum you'll see on a clock. The following graph shows the count for each sum of digits. You'll see that for a 12 hour clock the peak is at 11 and for a 24 hour clock the peak is at 12 with 11 being a close second.

For a 12 hour clock the probability that the sum of digits will be 128/1440 (or about 9% of the time). For a 24 hour clock it's 124/1440 (or about 9% of the time). So it's unsurprising that 11 comes up a lot here.

Another area of 11 craziness is airline seating. This is probably because people get freaked out by flying and look for patterns. Suppose you sit in economy on a British Airways long haul flight. You'll be sitting in a 747, 767 or 777. You then take your seat number add up the digits and then add the letter on using its place in the alphabet (e.g. sitting in 14F then you have 1 + 4 + 6 = 11). Using the British Airways seat maps you can compute the value of for each seat in economy:

On a 767 11 is the most frequently occurring sum, on a 747 it's 10 (with 11 close behind) and on a 777 11 is just beaten out by 12.

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