Question

Five measurements are made using a weighing machine, and the readings are 80 kg, 79 kg, 81 kg, 79 kg and 81 kg. The sample standard deviation of the measurement is ___________ kg (rounded off to two decimal places).

Hint:

For a {sample} standard deviation, divide by $n-1$ (Bessel’s correction), then take the square root.

Answer 1

Correct Answer: 0.98

Mean $\bar{x}=\dfrac{80+79+81+79+81}{5}=80$. Deviations: $0,-1,1,-1,1$; squared sum $=0+1+1+1+1=4$. Sample variance $s^2=\dfrac{4}{5-1}=1 \Rightarrow s=\sqrt{1}=1.00$ kg.