Answer
Lower Bound = 1612.46
Upper Bound = 2667.4
Work Step by Step
The normal probability plot and boxplot confirm that the data is normally distributed.
Here we have: n = 7, df = n-1 = 6, x̅ = 2139.93 and s = 1114.41
Confidence = 90%
α = 1 - 0.90 = 0.10, α/2 = 0.05, tα/2=1.771
$E=1.771 \times \frac{1114.41}{\sqrt 14} = 527.47$
Lower Bound = x̅ - E = 2139.93 - 527.47 = 1612.46
Upper Bound = x̅ + E = 2139.93 + 527.47 = 2667.4
