(Normal approximation to the Poisson distribution.)
Let X be Poisson with parameter As. Then, for large values of As, X is approximately normal with mean As and variance As. (The proof of this theorem is also based on the Central Limit Theorem and will be considered in Chap. 7.) Let X be a Poisson random variable with parameter As = 15. Find P[X 5 12] from Table II of App. A. Approximate this probability using a normal curve. Be sure to employ the half-unit correction factor.