Spinning is also not 50/50, on US pennies at least. If you give them very vigorous spins on a stable flat surface, tails comes up more often than heads. I have done both of these in class in the context of null hypothesis tests (setting null at .5); The last time I spun pennies I got 73 tails of 120 spins (61%). I asked a physicist here to explain the spinning bias years ago, but forgot the details. I vaguely remember his answer tied in with the bevel issue, but forgot the details.
============================================ John W. Kulig Professor of Psychology Plymouth State College Plymouth NH 03264 ============================================ Za dvumia zaitsami pogonish'sia - ni odnogo ne poimaesh' [If you chase after two rabbits, you won't catch even one]Russian proverb. > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Duncan Murdoch > Sent: Thursday, February 26, 2004 9:22 PM > To: [EMAIL PROTECTED] > Subject: Re: [edstat] tossing a coin is not a random process > > On 26 Feb 2004 15:56:41 -0800, in sci.stat.edu [EMAIL PROTECTED] (Dennis > Roberts) wrote: > > >A key "may be" in the minting process ... I heard once at a conference > >where a demo was done .. lining up coins on edge and pounding the table > ... > >that the p is not 50/50 for H and T to land face up ... that there is a > >slight bevel to the edge (not noticeable by eye) that makes ejecting from > a > >mold easier > > The bias for "tipping" coins like that is very noticeable. I do an > experiment on that in my intro stats course most years. As long as > the table is flat, and you don't hit it too hard, the probability of H > is around 0.4 with Canadian pennies. (This year's data was 130 H in > 345 tips.) > > Duncan Murdoch > . > . > ================================================================= > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at: > . http://jse.stat.ncsu.edu/ . > ================================================================= . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
