Atest for the level of potassium in the blood is not perfectly precise. moreover, the actual level of potassium in a person's blood varies slightly from day to day. suppose that repeated measurements for the same person on different days vary normally with sigma equals 0.02.
a) julie's potassium level is measured once. the result is x-bar = 3.4. give a 90% confidence interval for her mean potassium level.