Posted by Theresa on Wednesday, October 6, 2010 at 6:57pm.
How many students must we sample if we want to be within 4% of the true proportion of female students at DeVry University when using a 95% confidence interval?

Statistics  MathGuru, Wednesday, October 6, 2010 at 7:37pm
Try this formula:
n = [(zvalue)^2 * p * q]/E^2
= [(1.96)^2 * .5 * .5]/.04^2
I'll let you finish the calculation. Round to the next highest whole number.
Note: n = sample size needed; .5 for p and .5 for q are used if no value is stated in the problem. E = maximum error, which is .04 (4%) in the problem. Zvalue is found using a ztable (for 95%, the value is 1.96).