posted by Theresa on .
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?
Try this formula:
n = [(z-value)^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. Z-value is found using a z-table (for 95%, the value is 1.96).