Help!! Please help me to understand (work out) how to do this problem. And if po
ID: 3150671 • Letter: H
Question
Help!! Please help me to understand (work out) how to do this problem. And if possible the steps how to do it in Excel. Thank you!
2. A local business is interested in the opinion of its customers as to the effectiveness of its
product. There is no past data as to this effectiveness and no guess that has any degree of
basis. How large of sample of customers is needed to assure the error will be no greater than
20% with a 95% confidence?
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Explanation / Answer
Note that
n = z(alpha/2)^2 p (1 - p) / E^2
where
alpha/2 = 0.025
As there is no previous estimate for p, we set p = 0.5.
Using a table/technology,
z(alpha/2) = 1.959963985
Also,
E = 0.2
p = 0.5
Thus,
n = 24.00911763
Rounding up,
n = 25 [ANSWER]
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