it's very easy to use your ti-84 to find critical values for proportions again for proportions we're going to go two seconds VARs and choose inverse normal all we have to know is our level of confidence so for instance if it's a 90% confidence interval I'm going to enter in point 9 keep my mean at zero and my standard deviation at 1 and choose Center and then paste and it's going to give me the two critical values the negative side and the positive side and we only care about the positive 1.645 I could do the same thing if I were trying to find say a 95% confidence interval I would just change it to 95 and then paste and again as long as you have it on Center you should be good to go so 1.96 and again those should all match up to what we have found before