Simple Random Sampling

simple random sample

Draw a sample of size n from a population of size N such that every possible sample of size n has the same probability of being selected.

What does simple random sampling assure

• that each individual element in the population has an equal chance of being selected in the sample

• selected elements are mutually independent

multinomial distribution

models situations where each trial results in one of k categories

• each trial can fall in one of k categories instead of only two outcomes (binomial distribution)

marginal distribution of multinomial distribution

each individual category count follows a binomial distribution

if we focus on the sum of two categories what is the distribution?

It is also binomial