Answer
$t_0\lt -t_α$: null hypothesis is rejected.
There is enough evidence to conclude that the mean temperature of humans is less than 98.6°F.
Work Step by Step
$H_0:~µ=98.6°F$ versus $H_1:~µ\lt98.6°F$
Requirement:
$n\geq30$
$n=700$, so:
$d.f.=n-1=699$
Left-tailed test:
$t_0=\frac{x ̅-µ_0}{\frac{s}{\sqrt n}}=\frac{98.2-98.6}{\frac{0.7}{\sqrt {700}}}=-15.119$
$t_α=t_{0.01}=2.330$
(According to Table VI, for d.f. = 1000, the closest value to 699, and area in right tail = 0.01)
So, $-t_α=-2.330$
Since $t_0\lt -t_α$, we reject the null hypothesis.
