Question

In the United States, 1000 residents aged 15 or older were surveyed and 870 replied that they were satisfied with the water quality. The 90% confidence interval estimate of all U.S residents satisfied with their water quality is _________.

Answer 1

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.

Step-by-step explanation:

The formula to find the interval of confidence level is as below

`=(p^(\prime)-z*\sqrt[]{(p^(\prime)(1-p^(\prime)))/(n)},\text{p' }+z*\sqrt[]{(p^(\prime)(1-p^(\prime)))/(n)})`

Now we have to find the value of all

z=1.64485

p'=870/1000=0.87

n=1000

Now put the all values

`(0.87-1.64485*\sqrt[]{(0.87(1-0.87))/(1000)},0.87+1.64485*\sqrt[]{(0.87(1-0.87))/(1000)})`
`(0.87-0.0175,0.87+0.0175)`
`(0.8525,0.8875)`

Final answer:

Confidence interval is (0.8525,0.8875)