Answer
$k\lt critical~value$: null hypothesis is rejected.
There is enough evidence to conclude that the median number of hours that students study each week is less than 15.
Work Step by Step
$H_0:~M=15$ versus $H_1:~M\lt15$
$number~of~plus~signs=4$
$number~of~minus~signs=15$
$n=4+15=19$ (small sample)
$Critical~value=5$
(According to table XI, for $n=19$ and $α=0.05$ (one tail))
Left-tailed test:
$k=number~of~plus~signs=4$
Since $k\lt critical~value$, we reject the null hypothesis.
