Question 1043436: The table to the right shows the results of a survey in which 2566 adults from Country A, 1128 adults from Country B, and 1085 adults from Country C were asked if human activity contributes to global warming. Complete parts (a), (b), and (c).
Adults who say that human activity contributes to global warming
Country A
68%
Country B
86%
Country C
93%
(a) Construct a 99% confidence interval for the proportion of adults from Country A who say human activity contributes to global warming. Round to three decimal places as needed.
(b) Construct a 99% confidence interval for the proportion of adults from Country B who say human activity contributes to global warming. Round to three decimal places as needed.
(c) Construct a 99% confidence interval for the proportion of adults from Country C who say human activity contributes to global warming. Round to three decimal places as needed.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The CI for each is of the form z*sqrt {(p)(1-p)/n}, and that is added/subtracted to the point estimate
For A
2.576*sqrt (0.68)(0.32/2566; the sqrt term is 0.0092, and the product is 0.024
The CI is (0.656,0.704)
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B has a smaller number, a higher probability, but n is a lot less, so expect a slightly larger CI
2.576*sqrt(0.86)(0.14)/1128; sqrt term is 0.0103, and the product is 0.0266
(0.833,0.886)
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C has about the same number as B and a probability further from 50%, which will tend to lower the CI.
2.576*sqrt{(0.93)(0.07)/1085}; sqrt term is 0.0077, and the product is 0.020
(0.910,0.950)
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Can use calculator STAT then TESTS, then 1-prop z-interval
You need the number for each, and 68% of A is 1745, 86% of B is 970 and 93% of C is 1009. These can be entered and the CI of 0.99 will be computed.
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