Answer:
(0.649,0.691)
Step-by-step explanation:
Basically that is a problem about confidence Interval for a Popuplation Mean.
The formula for confidence interval is given by,
[tex]ci= \bar{x} \pm t*\frac{s}{\sqrt{n}}[/tex]
Degree of Freedom,
[tex]DF = 15-1 = 14[/tex]
The T-Table say that for 80% ci and DF = 14 the value of t must be 1.345.
[tex]ci = 0.670 \pm 1.345*\frac{0.0616}{\sqrt{15}}[/tex]
[tex]ci = 0.670 \pm 0.021[/tex]
[tex](0.649,0.691)[/tex]
