Answer
$k\gt critical~value$: null hypothesis is not rejected.
There is not enough evidence to conclude that the median age at which women marry in Cook County, Illinois, is less than the median age throughout the United States.
Work Step by Step
$H_0:~M=25.8$ versus $H_1:~M\lt25.8$
$number~of~plus~signs=9$
$number~of~minus~signs=11$
$n=9+11=20$ (small sample)
$Critical~value=5$
(According to table XI, for $n=20$ and $α=0.05$ (one tail))
Left-tailed test:
$k=number~of~plus~signs=9$
Since $k\gt critical~value$, we do not reject the null hypothesis.
