Question 1187309
90% half-interval is a t(0.95, df=819)=1.645* s/sqrt(n). This is essentially z, but when there is a sample with a sample sd, t should be considered, and then with a large sample size use z.
interval is 1.645*13.6/sqrt(820)=0.78
the 90%CI is (61.82, 62.38) mm Hg
or (61.8 < mu < 62.4) mm Hg