Juan makes a measurement in a chemistry laboratory and records the result in his
ID: 3385842 • Letter: J
Question
Juan makes a measurement in a chemistry laboratory and records the result in his lab report. The standard deviation of students' lab measurements is = 13 milligrams. Juan repeats the measurement 4 times and records the mean x¯ of his 4 measurements.
What is 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¯ 's?)
How many times must Juan repeat the measurement so that the standard deviation of x¯ is 3? (Round your answer to the nearest whole number.)
Explanation / Answer
Juan makes a measurement in a chemistry laboratory and records the result in his lab report. The standard deviation of students' lab measurements is = 13 milligrams. Juan repeats the measurement 4 times and records the mean x¯ of his 4 measurements.
What is 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¯ 's?)
Sd=sd/sqrt(n) = 13/sqrt(4) =6.5
How many times must Juan repeat the measurement so that the standard deviation of x¯ is 3? (Round your answer to the nearest whole number.)
Sd=sd/sqrt(n) = 13/sqrt(n) =3
n=132/32 =18.777
answer = 19
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