## Elementary Statistics (12th Edition)

$\alpha=1-0.98=0.02.$ $\sigma$ is 42.3, hence we use the z-distribution with $df=sample \ size-1=16-1=15$ in the table. $z_{\alpha/2}=z_{0.01}=2.33.$ Margin of error:$z_{\alpha/2}\cdot\frac{\sigma}{\sqrt {n}}=2.33\cdot\frac{42.3}{\sqrt{16}}=24.64.$ Hence the confidence interval:$\mu$ is between 98.9-24.64=74.26 and 98.9+24.64=125.54. The result suggests that the mean wakeup time is likely because it is in the interval and that zopi-cloning doesn't seem to be effective, because it is not more then the upper bound.