## Cannot understand some mathematical notation/symbols.

For the discussion of math. Duh.

Moderators: gmalivuk, Moderators General, Prelates

### Cannot understand some mathematical notation/symbols.

Can someone please explain how/what P(k; N) is/works and also , or at least what it's called? I can't seem to find anything about it and i have no idea what it is.

These are from here btw

http://en.wikipedia.org/wiki/Random_wal ... rtionality

>-)

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### Re: Cannot understand some mathematical notation/symbols.

I would recommend you look into binomial coefficients:
http://en.wikipedia.org/wiki/Binomial_coefficient
zeitpfeil

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### Re: Cannot understand some mathematical notation/symbols.

P(k; N) is the probability of getting k heads from N tosses of a fair coin.
\begin{pmatrix}N\\k\end{pmatrix} counts the number of ways of choosing k of N objects, e.g. if you flipped a coin 8 times in a row, there would be \begin{pmatrix}8\\5\end{pmatrix} ways for 5 of the flips to come out heads (and the rest to come out tails).
The formula
P(k; N)=\begin{pmatrix}N\\k\end{pmatrix}\frac{1}{2^N}
comes from the fact that there are \begin{pmatrix}N\\k\end{pmatrix} sequences of N coin flips with k heads, and each sequence having probability 1/2N.
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.

"With math, all things are possible." —Rebecca Watson

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### Re: Cannot understand some mathematical notation/symbols.

Would i be correct to say that
N choose k = (N!)/(k!*(N-k)!)
except when k is bigger than N at which point N choose k = 0
>-)

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### Re: Cannot understand some mathematical notation/symbols.

Yes, that is a correct formula for N choose k (as long as N and k are nonnegative integers).
++\$_
Mo' Money

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### Re: Cannot understand some mathematical notation/symbols.

It's also often notated (at least, around here) as NCk.
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eSOANEM

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### Re: Cannot understand some mathematical notation/symbols.

Really annoying, in Dutch you'd say "N over k", while in English that usually implies division.. aarrgh