Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » sci.math.* » sci.math.independent

Topic: say I flip a coin 100 times...
Replies: 46   Last Post: Apr 18, 2005 9:42 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
George Greene

Posts: 448
Registered: 12/12/04
Re: say I flip a coin 100 times...
Posted: Apr 12, 2005 10:05 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply


HERC777 wrote:
> there's about 1,000,000 combinations of a sequence of 20 coin flips
> 2^10 = 1024
> 2^20 = a million
>
> so on average they should copy your sequence up to the 1st 20 flips..
>
> Agree?


No. Jesus.
First of all, you have to know what you are
averaging OVER. You are overaging over FLIPPERS,
or flip-sequences. You are averaging over a million
things. For each of these million strings (of H or T),
you want to know how long its prefix-matching-you is.
The number of flippers matching-you-so-far starts out
at a million after 0 flip-positions and falls by half
with every flip(in time) thereafter. Half the million
will flip opposite from you on the first flip and so
will have a prefix-matching-you of length 0.
1/4 of them will match you on the first flip and
miss on the 2nd, and have a match-you length of 1.
1/8 of them will match you on the first two but miss
on the 3rd, and have a match-you length of 2.
On the 20th flip, the EXPECTED number of flippers
continuing to match you all this way will be less than 1.
Furthermore, the AVERAGE, over all flippers, of the
initial-length-of-match-you-prefix, is ALSO
LESS THAN 1.

NOT 20.

This is HIGH SCHOOL algebra, herc.



Date Subject Author
4/12/05
Read say I flip a coin 100 times...
HERC777
4/12/05
Read Re: say I flip a coin 100 times...
Jan Burse
4/12/05
Read Re: say I flip a coin 100 times...
HERC777
4/12/05
Read Re: say I flip a coin 100 times...
George Greene
4/13/05
Read Re: say I flip a coin 100 times...
Glenn C. Rhoads
4/13/05
Read Re: say I flip a coin 100 times...
Barb Knox
4/13/05
Read Re: say I flip a coin 100 times...
HERC777
4/13/05
Read Re: say I flip a coin 100 times...
Yajun
4/13/05
Read Re: say I flip a coin 100 times...
HERC777
4/13/05
Read Re: say I flip a coin 100 times...
Jay
4/13/05
Read Re: say I flip a coin 100 times...
HERC777
4/13/05
Read Re: say I flip a coin 100 times...
Jay
4/14/05
Read Re: say I flip a coin 100 times...
Yajun
4/14/05
Read Re: say I flip a coin 100 times...
George Greene
4/14/05
Read Re: say I flip a coin 100 times...
George Greene
4/13/05
Read Re: say I flip a coin 100 times...
Will Twentyman
4/13/05
Read Re: say I flip a coin 100 times...
briggs@encompasserve.org
4/13/05
Read Re: say I flip a coin 100 times...
briggs@encompasserve.org
4/14/05
Read Re: say I flip a coin 100 times...
George Greene
4/14/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/14/05
Read Re: say I flip a coin 100 times...
briggs@encompasserve.org
4/12/05
Read Re: say I flip a coin 100 times...
Tony
4/13/05
Read Re: say I flip a coin 100 times...
HERC777
4/13/05
Read Re: say I flip a coin 100 times...
ken quirici
4/13/05
Read Re: say I flip a coin 100 times...
Ralph Hartley
4/13/05
Read Re: say I flip a coin 100 times...
Robert Low
4/13/05
Read Re: say I flip a coin 100 times...
Ralph Hartley
4/13/05
Read Re: say I flip a coin 100 times...
Robert Low
4/13/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/13/05
Read Re: say I flip a coin 100 times...
HERC777
4/13/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/14/05
Read Re: say I flip a coin 100 times...
HERC777
4/14/05
Read Re: say I flip a coin 100 times...
George Greene
4/14/05
Read Re: say I flip a coin 100 times...
HERC777
4/15/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/15/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/16/05
Read Re: say I flip a coin 100 times...
George Greene
4/16/05
Read Re: say I flip a coin 100 times...
HERC777
4/17/05
Read Re: say I flip a coin 100 times...
George Greene
4/17/05
Read Re: say I flip a coin 100 times...
Patricia Shanahan
4/17/05
Read Re: say I flip a coin 100 times...
HERC777
4/18/05
Read Re: say I flip a coin 100 times...
Patricia Shanahan
4/17/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/18/05
Read Re: say I flip a coin 100 times...
HERC777
4/18/05
Read Re: say I flip a coin 100 times...
George Greene
4/18/05
Read Re: say I flip a coin 100 times...
tchow@lsa.umich.edu
4/18/05
Read Re: say I flip a coin 100 times...
HERC777

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.