Answer
-10.506 to -3.494
Work Step by Step
df = n - 1 = 16 - 1 = 15
$t_{α/2} = 0.05$
From student's t distribution table, we have:
$t_{0.05} = 1.753$
$E = 1.753 . \frac{8}{\sqrt 16} = 1.753 . 2 = 3.506$
Confidence interval will be:
$\bar d - E = -7 - 3.506 = -10.506$
$\bar d - E = -7 + 3.506 = -3.494$
