She doesn't know what this is so she is going to take a sample size of size n and in fact this question is all about what n does she need in order to have the desired margin of error. Well whatever sample she takes there she's going to calculate a sample proportion and then the confidence interval that she's going to construct is going to be that sample proportion plus or minus critical value and this critical value is based on the confidence level. We'll talk about that in a second. What z-star, what critical value would correspond to a 95% confidence level times and then you would have times the standard error of her statistic and so in this case it would be the square root. It would be the standard error of her sample proportion which is the sample proportion times one minus the sample proportion, all of that over her sample size. Now she wants the margin of error to be no more than 2%. So the margin of error is this part right over here.