Question 4.34: The number of hits on a website follows a Poisson distributi...

Let X denote the number of hits on the website in three hours. The mean number of hits in three hours is 81, so X∼ Poisson(81). Using the normal approximation, we find that X ∼ N(81, 81). We wish to find P(X ≥ 90). We compute the z-score of 90, which is

z=\frac{90-81}{\sqrt{81}}=1.00

Using the z table, we find that P(X ≥ 90) = 0.1587 . See Figure 4.24.