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Subject: [OT] - probability algorithm question

Author: Andrew Dados

Date: 06:44:52 12/31/01



Suppose I am getting tons of scores for some experiment which outcome will obey
known distribution (In my problem it is Poisson distribution; type of
distribution should not matter).

I can't store all scores, but I need to know average and mean parameters, so I
could recreate distribution function at some time later. How can I store some
set of data as small as possible to be able to add new scores to it and still
get my mean/sigma right?

Example: One experiment is 1000 tosses of a coin. In this case outcome is number
of heads. I will collect unspecified number of such results. In this case I
could simply store an array of 1000 counters, but I can't afford it. Average
number can be easily stored and incrementally updated with 2 ints: total sum and
number of experiments. Can some similar trick be done to recalculate mean value
after new score comes in?

Chess example (closer to my problem): I have a chess position for which I am
getting time-to-solve results from many players. So their rating distribution is
'predefined' here. The more samples I will collect, the more accurately I can
assing a rating for some new player solving this position. I can not collect all
separate times-to-solve. So for each player I need to update some totals to be
able to calculate mean from those totals (average is easy). Can this be
accurately done?

..and no... while it sounds like that - it is not some school assignment. :)

-Andrew-



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