Rain in Gheisra - day 3

pattern 3

you chose random... you are wrong

the rain drops are too uniform

A common problem is that we believe random things are more uniform than they are. This is true on average for large numbers of things, but when we are dealing with relatively small numbers things are typically far more uneven.

In this pattern there are exactly 5 rain drops on every tile. It is just possible that this happened by chance - but extremely unlikely. In fact, it was deliberately generated to have exactly the same number of rain drops in each square, although otherwise is completely random.

This is an example where there is no non-uniformity or bias in the average distribution, but a correlation between the outcomes of different trials. effectively each raindrop avoided 'overcrowded' tiles!

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tutorial outline

tutorial notes

7 common errors

book list

rainfall in Gheisra

two-horse races

more coin tossing!

HyperCard demo

other tutorials by Alan

about the stats tutorial

links elsewhere



Alan Dix 5/8/98