Belgian euro coins: 140 heads in 250 tosses - suspicious?

David J C MacKay

A statistical statement appeared in The Guardian on Friday January 4, 2002:

When spun on edge 250 times, a Belgian one-euro coin came up heads 140 times and tails 110. ``It looks very suspicious to me," said Barry Blight, a statistics lecturer at the London School of Economics. ``If the coin were unbiased the chance of getting a result as extreme as that would be less than 7%."

But do these data give evidence that the coin is biased rather than fair? This one-page document gives the answer.

postscript (Cambridge UK) | postscript (Canada mirror).

pdf (Cambridge UK). | pdf (Canada mirror).

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@techreport{MacKayEuro2002,
author={David J. C. MacKay},
title={Belgian euro coins: 140 heads in 250 tosses - suspicious?},
institution={University of Cambridge, Department of Physics},
url={http://www.inference.phy.cam.ac.uk/mackay/abstracts/euro.html},
year={2002}
}

related publications.
David MacKay's: home page, publications. bibtex file.
Canadian mirrors: home page, publications. bibtex file.