For Finite Sample Size. Necessary Sample Size Z-score2 StdDev 1-StdDev margin of error2. Z 2 p 1-p c 2.
603 respondents are needed and that becomes your sample size.
N z 2 p 1 - p e 2 where z 1645 for a confidence level a of 90 p proportion expressed as a decimal e margin of error. SS fracZ2P1-PC2 Where SS Sample Size. The formula does not cover finite population. N z 2 p 1 - p e 2 where z 1645 for a confidence level a of 90 p proportion expressed as a decimal e margin of error.