Combinatorics

Abstract

In this chapter we will study certain types of random selection within a uniform model. Such samples can occur when we select a representative from an audience, when we sample for errors, play lotteries, or generally when we choose between alternatives which are equally probable. The main problem is then to figure out how many combinations there are of a particular type. When we know the number of combinations, it is easy to figure out the probabilities, since in a uniform model all alternatives are equally probable. We then find the probability as the fraction between the number of combinations of the type we are looking for and the number of combinations in total.