Statistics: What is the difference between a Binomial and Poisson distribution?

Binomial:

1. A single trial has only 2 possible outcomes: success or failure

2. A fixed number of trials, n

3. Trials are independent

4. The probability of success remains constant at each trial

Mean: E(x) = np      Var(x) = np(1-p)

Poisson:

1. events must occur singly - 2 cannot occur simultaneously

2. uniformly - events occur at a constant rate

3. independently - occurence of one event does not influence another

mean = variance