Answer
We can say with 99% confidence that the mean number of children of all couples who have been married 7 years is between 1.85 and 2.689.
Work Step by Step
Here we have n = 60, df = n-1 = 59, x̅ = 2.27 and s = 1.22
Confidence = 99%
α = 1 - 0.99 = 0.01, α/2 = 0.005, $t_{α/2} = 2.66$
$E = 2.66 \times \frac{1.22}{\sqrt 60} = 0.419 $
Lower Bound = x̅ - E = 2.27 - 0.419 = 1.85
Upper Bound = x̅ + E = 2.27 - 0.315 = 2.689
We can say with 99% confidence that the mean number of children of all couples who have been married 7 years is between 1.85 and 2.689.
