### Author Topic: Spinning penny  (Read 2703 times)

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#### TXCraig1

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##### Spinning penny
« on: November 07, 2012, 08:52:17 PM »
If you spin a penny on a flat surface and let it slown and fall over by itself, what is the probability it will land heads up?

Don't Google or anything. Just post what you think.

Thanks.
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#### Tscarborough

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##### Re: Spinning penny
« Reply #1 on: November 07, 2012, 08:58:46 PM »

#### Tscarborough

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##### Re: Spinning penny
« Reply #2 on: November 07, 2012, 09:01:21 PM »
Assuming the new penny that is, I would think an Ol' Abe would be about the same to tails.

#### Chicago Bob

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##### Re: Spinning penny
« Reply #3 on: November 07, 2012, 09:04:46 PM »
Assuming the new penny that is, I would think an Ol' Abe would be about the same to tails.
+1
Yep, 'ol Abe was honest. No rigged game with the "Railsplitter".
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#### Chicago Bob

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##### Re: Spinning penny
« Reply #4 on: November 07, 2012, 09:14:51 PM »
Craig,
Is the probability result the same for any U.S. denomination coin?
"Care Free Highway...let me slip away on you"

#### pizzaneer

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##### Re: Spinning penny
« Reply #5 on: November 07, 2012, 09:32:28 PM »
Theoretically, it should be exactly 50/50.

In real life, no surface is flat, there are always pits and gouges on the coin rim, and there is always random air movement, and lets not even get into the launching mechanism.  Any or a combination of these factors can make it possible to cheat the odds.

I'd rather eat one good meal a day than 3 squares of garbage.

#### TXCraig1

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##### Re: Spinning penny
« Reply #6 on: November 07, 2012, 09:53:37 PM »
Any other thoughts?
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#### Chicago Bob

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##### Re: Spinning penny
« Reply #7 on: November 07, 2012, 09:59:16 PM »
Theoretically, it should be exactly 50/50.

In real life, no surface is flat, there are always pits and gouges on the coin rim, and there is always random air movement, and lets not even get into the launching mechanism.  Any or a combination of these factors can make it possible to cheat the odds.

But aren't these variances the very thing that creates "odds"..
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#### TXCraig1

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##### Re: Spinning penny
« Reply #8 on: November 07, 2012, 10:04:33 PM »
Theoretically, it should be exactly 50/50.

In real life, no surface is flat, there are always pits and gouges on the coin rim, and there is always random air movement, and lets not even get into the launching mechanism.  Any or a combination of these factors can make it possible to cheat the odds.

These factors should have a random effect, i.e. they wouldn't favor heads or tails, right?

Seriously, this was not a trick or nuanced question.

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#### Tscarborough

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##### Re: Spinning penny
« Reply #9 on: November 07, 2012, 10:04:44 PM »
Those variances do, but the relative weight of the sides of the coin throw it off for true random.  True random is almost impossible electronically, but possible using random coins to generate random H/T for example.  Pi is not random, FYI, since it will be the same every time you calculate it (unless your algorithm simply picks a random point in the sequence, in which case it is STILL not truly random.

#### TXCraig1

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##### Re: Spinning penny
« Reply #10 on: November 07, 2012, 10:06:42 PM »
Pi is not random, bit it is non-repeating. There is no pattern in it.
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#### Chicago Bob

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##### Re: Spinning penny
« Reply #11 on: November 07, 2012, 10:07:58 PM »
Those variances do, but the relative weight of the sides of the coin throw it off for true random.  True random is almost impossible electronically, but possible using random coins to generate random H/T for example.  Pi is not random, FYI, since it will be the same every time you calculate it (unless your algorithm simply picks a random point in the sequence, in which case it is STILL not truly random.
Thanks....OK then...which side is it "supposed" to fall on....
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#### Tscarborough

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##### Re: Spinning penny
« Reply #12 on: November 07, 2012, 10:15:38 PM »
There is certainly a pattern to Pi, here it is: 3.14159...  Works every single time you calculate it, exactly the same, no randomness what so ever.

It is unique, not random, there is a difference.

True random is best illustrated by "bookie numbers".  When a bookie wants to run an almost honest numbers game, he sets the numbers to something like box scores, placing horse numbers or something like that.  They are still biased numbers, but in general they appear to be random.
« Last Edit: November 07, 2012, 10:17:59 PM by Tscarborough »

#### Chicago Bob

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##### Re: Spinning penny
« Reply #13 on: November 07, 2012, 10:21:06 PM »
I think you are telling me the answer is 50/50.....but I don't get how you come up with .54
« Last Edit: November 07, 2012, 10:23:08 PM by Chicago Bob »
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#### Tscarborough

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##### Re: Spinning penny
« Reply #14 on: November 07, 2012, 10:27:29 PM »
Relative size of the raised surface of each side, thus more weight to that side.  In the long game, the coin will fall to it's heaviest side.

#### Chicago Bob

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##### Re: Spinning penny
« Reply #15 on: November 07, 2012, 10:36:31 PM »
I understood that from the start....just thought you were trying to show a different way of looking at it. So, if you don't mind my asking...how is it you know the split weight of a penny?
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#### Tscarborough

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##### Re: Spinning penny
« Reply #16 on: November 07, 2012, 10:46:07 PM »
By comparing the relative raised sides.  That is why an Abe penny is different from a current penny.

#### Jet_deck

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##### Re: Spinning penny
« Reply #17 on: November 07, 2012, 10:48:36 PM »
Not google-ing anything I picked up a penny and looked at it.  It appears, that on this penny, the head side is recessed a bit which makes the image stick out a bit without being "heavier".  The building and the writing on the back seems to lend itself to being heavier.  I will give it 5% heavier on the back.

I say 55% tails up.  If I am incorrect, I am heading straight for the 'what are you drinking' thread, and I will get that one right.
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#### Chicago Bob

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##### Re: Spinning penny
« Reply #18 on: November 07, 2012, 10:56:56 PM »
By comparing the relative raised sides.  That is why an Abe penny is different from a current penny.
By "Abe' penny I  assume then that the old penny's "wheat" side was/feels more raised/meatier... now I know that you are very good at "objects in space" and have, I'm sure, a more than normal touch/feel for things....please humor me with how you came to the .54 odds figure.
"Care Free Highway...let me slip away on you"