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

[zeitpfeil]

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

[skeptical scientist]

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 1/2^N.

[>-)]

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

[++$_]

Yes, that is a correct formula for N choose k (as long as N and k are nonnegative integers).

[eSOANEM]

It's also often notated (at least, around here) as ^NC_k.

[Tuinkabouter]

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