Chapter 9 - Section 9.2 - Assess Your Understanding - Applying the Concepts - Page 450: 36c

We are 95% confident that the mean tax paid for a 3-day business trip is between 73.07 and 93.63.

Here we have n = 8, df = n-1 = 7, x̅ = 83.35 and s = 12.32 Confidence = 95% α = 1 - 0.95 = 0.05, α/2 = 0.025, $t_{α/2} = 10.28$ $E = 2.36 \times \frac{12.32}{\sqrt 8} = 10.28 $ Lower Bound = x̅ - E = 83.35 - 10.28 = 73.07 Upper Bound = x̅ + E = 83.35 + 10.28 = 93.63