What is meant by ‘confidence level’ and why is it different than ‘confidence interval’? What is the difference between a ‘point estimate’ and a ‘confidence interval’? When trying to estimate a population mean, when will we use a z-value based confidence interval? When do we use a t-value based confidence interval? What is a ‘proportion’? 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?