• June 20th 2009, 03:08 PM
tennisair
We the fact that $T = \frac {\bar{X} - \mu}{S / \sqrt{n}}$ follows a t-distribution with n-1 degrees of freedom.
$\bar{x} \ \pm \ t_{(\alpha / 2, n-1)}\Big(\frac{s}{\sqrt{n}}\Big)$
$\Big[8.7 - t_{(0.025, 9)}\Big(\frac{3.3}{\sqrt{10}}\Big), \ 8.7 + t_{(0.025, 9)}\Big(\frac{3.3}{\sqrt{10}}\Big)\Big]$