That would be very cruel of me. The organizer numb...

2008-12-07T09:25:00.000Z

That would be very cruel of me. The organizer numbers have been changed. I don't think we should be surprised by the findings though, should we :)

Very cool! Who is organizer 4? Do I have to sear...

2008-12-06T21:02:00.000Z

Very cool! Who is organizer 4? Do I have to search around through my decommissioned computers for zone 4 to find the answer to this?

First, I'm certain its not about the total number ...

2008-12-04T10:59:00.000Z

First, I'm certain its not about the total number of heads or tails. Comparing that across the class would allow you to estimate the proportion of the class that cheated, but not to identify individuals.

I suspect therefore its about the number sequence itself. Probably the number of sequential strings of H or T.

If it were me I would convert the sequence in to numbers and then look at the distribution of these numbers. I would do this by listing the length of each 'run' of heads or tails in order.

E.g. HHTHTTHHTHTHHHT would become 2,1,1,2,2,2,1,1,1,3,1

Lets have a stab at the maths:

Once you have flipped your first coin, the probability of the second flip being different, and ending the 'run' is 50%. So we should see '1' occur about 50% of the time in our list. (In my above made-up list, it is 6/11 - not too bad!)

The probability of the second flip being the same is also 50%. And the probability of this 'run' ending on the next flip is 50%. This means the total probability of getting a run of length two is 25%. (In my made-up flips above, I had '2' 4/11 times, or 36% of the time. Oops!)

Similarly, the probability of getting a run of length n is (50%)^n.

All the lecturer needs to do is convert each student's list of coin flips in to the number sequence above and do a statistical test to understand whether the difference from the expected pattern is less than 5% likely to be down to chance (or similar). 200 coin flips should give about 100 numbers once converted, which seems to be a decent sample size.

Anyone want to chip in on what the statistical test should be?

By the way, here's another (probable) application of Benford's law to coin-flipping in the real world: http://paul.kedrosky.com/archives/2008/07/21/hedge_fund_test.html

(From a blog I highly recommend, by the way)

So, help me understand how this would apply to fak...

2008-12-03T17:12:00.000Z

So, help me understand how this would apply to fake coin flipping data?

Comments on Info Clarity: Spotting fraud in numbers

That would be very cruel of me. The organizer numb...

Very cool! Who is organizer 4? Do I have to sear...

First, I'm certain its not about the total number ...

So, help me understand how this would apply to fak...