the masses, in grams, of thirteen ball bearings taken at random from a batch are: 21.4, 23.1, 25.9, 24.7, 23.4, 24.5, 25.0, 22.5, 26.9, 26.4, 25.8, 23.2, 21.9. calculate a 95% confidence interval for the mean mass of the population, supposed normal, from which these masses were drawn? what is x2, the upper limit of the 95% confidence interval? enter your answer rounded to two decimal places. for example, if your answer is 12.345 then enter as 12.35 in the answer box.
