Company has n=5,000,000 customers that are using service X. We need to determine customer satisfaction with service X through phone survey.

Is there a formal way to determine optimal sample size (assuming that all calls will be answered)?

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- Jul 6th 2010, 09:56 AMlosm1Random sample and confidence intervals
Company has n=5,000,000 customers that are using service X. We need to determine customer satisfaction with service X through phone survey.

Is there a formal way to determine optimal sample size (assuming that all calls will be answered)? - Jul 7th 2010, 07:00 PMpickslides
What confidence and error width do you deisre in the sample size?

- Jul 8th 2010, 07:33 AMlosm1
95% confidence, i don't know what error width is. (you can choose any appropriate error, I'm interested in approach, not just result for this specific case)

- Jul 8th 2010, 02:10 PMpickslides
It's good you have identified the confidence level required. The error width will be how far either side of this you can allow for.

$\displaystyle 95\% \pm 3\%$ will require more samples than $\displaystyle 95\% \pm 5\%$

Have a read of this guy.

PEOD6/PD006: Determining Sample Size

There is a table at the bottom that will give you some numbers to consider.