Before You Conduct a Survey;
Follow these steps to determine how many completed surveys are necessary:
To determine how many invitations need to be distributed divide the above number by the anticipated response rate. For example, if you need 483 completed surveys and you anticipate a 30% response rate you need to mail 1,610 surveys (483/.3).
Sample size required if desired confidence interval and population size are known (p=.5)
Please enter a number in the Error Desired and Population Size fields then tab out of those fields to calculate.
Do not use commas or other formatting characters:
After You Have Conducted a Survey;
Follow these steps to determine how confident you can be in the data you have collected:
If you have a 3.5% confidence interval at the 95% confidence level the table is basically saying that if you conducted the same survey 100 times, 95 out of the 100 administrations should yield results within +/- 3.5% of the current number.