Answer
We are 95% confident that the mean Secchi disk measurement is between 48 and 67.6 inches
Work Step by Step
Here we have n = 12, df = n-1 = 11, x̅ = 57.8 and s = 15.4
Confidence = 95%
α = 1 - 0.95 = 0.05, α/2 = 0.025, $t_{α/2} = 2.2$
$E = 2.2 \times \frac{15.4}{\sqrt 12} = 9.8 $
Lower Bound = x̅ - E = 57.8 - 9.8 = 48
Upper Bound = x̅ + E = 57.8 + 9.8 = 67.6
Hence, we are 95% confident that the mean Secchi disk measurement is between 48 and 67.6 inches.
