Juan makes the measurement in chemistry laboratory and records the result in his lab report. The standard deviation of students' lab measurements is standard deviation= 12 milligrams. Juan repeats measurement four times and records the mean xbar of his 4 measurements.
Determine the standard deviation (±0.01) of Juan's mean result? (That is, if Juan kept on making 4 measurements and averaging them, what would be the standard deviation of all his x bar's?)
How many times must Juan repeat the measurement so that the standard deviation of xbar is 3?