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'What Does Random Look Like?' printed from http://nrich.maths.org/

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On a strip like the one below, ask a friend to make up a sequence of twenty Hs and Ts that could represent a sequence of heads and tails generated by a fair coin, and ask them to write "made up" lightly in pencil on the back of the strip.
 
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Then ask your friend to flip a fair coin twenty times and record the results on a second strip, and this time ask them to write "real" lightly in pencil on the back.
 
Take the two strips and try to work out which was real and which was made up - you could create similar strips and challenge your friend in the same way.
 
Here is an animation which generates twenty random coin flips. Hover over the bars on the bar chart to see how the runs have been counted.
 
This text is usually replaced by the Flash movie.

Use the animation to generate several sequences of twenty coin flips, and try to get a feel for the features you would expect a random sequence to have.

How would you analyse whether a sequence came from a real coin?
Send us your ideas and justify the method you use to decide.

Are you now better at spotting fakes? Ask your friend to create two more strips and see if you can find the truly random one.