Juan makes a measurement in a chemistry laboratory and records the result in his lab report. the standard deviation of students' lab measurements is σ = 10 milligrams. juan repeats the measurement 3 times and records the mean x⎯⎯⎯ of his 3 measurements. (a) what is the standard deviation of juan's mean result? (that is, if juan kept on making 3 measurements and averaging them, what would be the standard deviation of all his x⎯⎯⎯′s? ) (b) how many times must juan repeat the measurement to reduce the standard deviation of x⎯⎯⎯ to 2.5? (a) 5.77 (b)