Answer
We are 99% confident that the mean number of books that Americans read either all or part of during the preceding year is between 12.05 and 14.75.
Work Step by Step
Here we have n = 1006, df = n-1 = 1005, x̅ = 13.4 and s = 16.6
Confidence = 99%
α = 1 - 0.99 = 0.01, α/2 = 0.005, $t_{α/2} = 2.581$
$E = 2.581 \times \frac{16.6}{\sqrt 1006} = 1.35 $
Lower Bound = x̅ - E = 13.4 - 1.35 = 12.05
Upper Bound = x̅ + E = 13.4 + 1.35 = 14.75
