Margin of error

Question

A research institute poll asked respondents if they felt vulnerable to identity theft. In the poll, n=1009 and x=531 Who said "yes". Use a 95% confidence level.  Identify the value of the margin or error E

Answer 1

In order to calculate this you need to know the standard deviation. P = 531/1009 = .5262. The formula for the standard deviation = sqr( p*q/n) which would be .0157. The 95% confidence interval would be 1.94* .0157= .03

 

The margin of error is pretty small because the sample size is so big. What this says is that the population percentage is somewhere between .5262 +/-.03