#### Answer

$H_0: \mu = 0$
$H_1: \mu>0$
Test statistic: .133
$P>.1$, so don't reject the hypothesis.

#### Work Step by Step

We want to see if the mean change is greater than 0, so we know $H_0: \mu = 0$
and $H_1: \mu>0$. We now use a Ti-84 calculator. To solve, go to "Stat," then "Tests," and then select "Stats." Next, plug in 0 for $\mu_0$, .4 in for $\bar{x}$, 21 for $Sx$, and 49 for n. Then, select "$>\mu_0$" and push calculate. Doing this, we find that the test statistic, t, is .133. From this, we can find that $P>.1$, so we cannot reject the hypothesis.