Answer :
Given:
Here In the United States, 1000 residents aged 15 or older were surveyed and 870 replied that they were satisfied with the water quality is given.
Required:
Interval of 90% confidence level.
Explanation:
The formula to find the interval of confidence level is as below
[tex]=(p^{\prime}-z*\sqrt[]{\frac{p^{\prime}(1-p^{\prime})}{n}},\text{p' }+z*\sqrt[]{\frac{p^{\prime}(1-p^{\prime})}{n}})[/tex]Now we have to find the value of all
z=1.64485
p'=870/1000=0.87
n=1000
Now put the all values
[tex](0.87-1.64485*\sqrt[]{\frac{0.87(1-0.87)}{1000}},0.87+1.64485*\sqrt[]{\frac{0.87(1-0.87)}{1000}})[/tex][tex](0.87-0.0175,0.87+0.0175)[/tex][tex](0.8525,0.8875)[/tex]Final answer:
Confidence interval is (0.8525,0.8875)