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Experience:  B.S. Mechanical Engineering
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# A cell phone manufacturer would like to know what proportion

### Resolved Question:

A cell phone manufacturer would like to know what proportion of its customers is dissatisfied with the service received from their local distributor. The customer’s relations department will survey a random sample of customers and compute a 99% confidence interval for the proportion that are dissatisfied. Form past studies they believe that this portion will be about 0.1. find the sample size needed if the margin of error of the confidence interval is to be about 0.015. suppose 15% of the sample say they are dissatisfied. What is the margin of error of the 99% confidence interval?
Submitted: 6 years ago.
Category: Homework
Expert:  abozer replied 6 years ago.
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abozer :

Hi,

Customer :

hello

abozer :

n ≥ p(1 - p)(z/E)^2

abozer :

substitute p = 0.1

abozer :

z = 2.576

abozer :

and

abozer :

E = 0.015

abozer :

n ≥ 0.1(1 - 0.1)(2.576/0.015)^2

abozer :

n ≥ 2654.3

abozer :

round it up to the next integer,

abozer :

n = 2655

abozer :

Margin of Error = z*sqrt(p(1 - p)/n)

abozer :

The sample size is required to answer this part of the question.

Customer :

ok how can i find the sample size

abozer :

It should be given in the question.

abozer :

Unless the question is asking us to use the sample size we found in part A.

abozer :

It doesn't say so but it could be.

Customer :

thats where i got stuck

abozer :

If so then the margin of error doesn't change.

abozer :

It is 0.015