Chapter 9 - Section 9.2 - Assess Your Understanding - Applying the Concepts - Page 449: 33

We are 95% confident that the mean incubation period of the SARS virus patients is between 1.08 and 8.12 days.

Here we have n = 81, df = n-1 = 80, x̅ = 4.6 and s = 15.9 Confidence = 95% α = 1 - 0.95 = 0.05, α/2 = 0.025, $t_{α/2} = 1.99$ $E = 1.99 \times \frac{15.9}{\sqrt 81} = 3.516 $ Lower Bound = x̅ - E = 4.6 - 3.516 = 1.08 Upper Bound = x̅ + E = 4.6 + 3.516 =8.12