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)?
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)?
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.