As mentioned in this section, when n is large, p is small, and np … 7, the Poisson probability distribution provides a good approximation to the binomial probability distribution.

Since we provide exact binomial probabilities

(Table I in Appendix B) for relatively small values of n, you can investigate the adequacy of the approximation for n = 30. Use Table I to find p102, p112, and p122 for n = 30 and p = .05. Calculate the corresponding Poisson approximations, using l = m = np. [Note: These approximations are reasonably good for n as small as 30, but to use such an approximation in a practical situation we would prefer to have n Ú 100.]