Copyright © University of Cambridge. All rights reserved.
'Can't Find a Coin?' printed from http://nrich.maths.org/
Imagine your teacher has set you the homework task of throwing a
coin 100 times and carefully recording your results in the order
that they appear. Imagine that you can't be bothered to go and find
a coin - the task is just too tedious. So you decide to try to fool
How will you go about it?
If you can see this message Flash may not be working in your browser
Please see http://nrich.maths.org/techhelp/#flash to enable it.
If you have managed to fool the teacher twice in a row, tell us how
you did it.
One of these students made up their homework results, which one is
the most suspicious?
Whilst all combinations of Heads and Tails are equally likely,
certain sets of results (such as all heads or alternating Heads and
Tails all the way) would look rather suspicious. Why is this?
The computer here is programmed to determine whether the set of
Heads and Tails falls into a suspicious category or not. Rather
interestingly, if you do generate the Heads and Tails truly
randomly using a coin then there is a 95% chance the the computer
will know that these were generated randomly. Don't believe it? Try