Antonio measures the alcohol content of whiskey for his Chemistry 101 lab. He actually measures the mass of 4 milliliters of whiskey -- a chemical calculation then finds the percent alcohol from the mass. The standard deviation of students' measurements of mass is = 10.4 milligrams (mg). Antonio repeats the measurement 3 times and records the mean of his 3 measurements.
(a) What is the standard deviation (sigma,Xbar) of Antonio's mean result?
(b) How many times must Antonio repeat the measurement to reduce the standard deviation of X(bar) to 2.48 mg?