If n=440 and ˆpp^ (p-hat) =0.75, find the margin of error at a
99% confidence level.
As in the reading, in your calculations:
--Use z = 1.645 for a 90% confidence interval
--Use z = 2 for a 95% confidence interval
--Use z = 2.576 for a 99% confidence interval.
Give your answer rounded to three decimal places.
Solution =
Given,
n = 440 ....... Sample size
= 0.75
Our aim is to construct 99% confidence interval.
c = 0.99
= 1 - c = 1- 0.99 = 0.01
/2 = 0.005 and 1- /2 = 0.995
Search the probability 0.995 in the Z table and see corresponding z value
= 2.576
Now , the margin of error is given by
E = /2 *
= 2.576 * [ 0.75 *(1 - 0.75)/ 440]
= 0.053
Answer :
The margin of error is 0.053
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