# How large should my survey be?

• Apr 28th 2008, 07:20 AM
chopet
How large should my survey be?
I need to conduct a 10min long marketing survey with 6 to 7 questions . How large should my sample size be to have results representative of a 1000000-large population group, considering I want to achieve a 95% confidence level?

$\displaystyle n = ({z \sigma \over E })^2$

but how can I reconcile the concept of a questionnaire with the standard deviation of the sample population $\displaystyle \sigma$ and the error E? Is there even a mean or proportion to talk about? The only unambiguous part is z = 1.96 for 95% confidence.
• Apr 29th 2008, 04:00 AM
mr fantastic
Quote:

Originally Posted by chopet
I need to conduct a 10min long marketing survey with 6 to 7 questions . How large should my sample size be to have results representative of a 1000000-large population group, considering I want to achieve a 95% confidence level?

$\displaystyle n = ({z \sigma \over E })^2$
but how can I reconcile the concept of a questionnaire with the standard deviation of the sample population $\displaystyle \sigma$ and the error E? Is there even a mean or proportion to talk about? The only unambiguous part is z = 1.96 for 95% confidence.