I don't understand when to use the poisson formula instead of the binomial formula (assuming that there's only two formulae to choose from).
The notes say that you use poisson when "you wish to count the number of times an event occurs in a given area of opportunity". But I don't have a clue what that means! So the question is when do I use poisson and when do I use binomial?
Sorry for spelling the title wrong! I can't change it now apparently. Who knows what "possion" is....