Answer to Question #85444 in General Chemistry for sam

Question

A researcher measures the mass of a beaker four times and obtains the following information:

Trial Mass (g)
1 12.001
2 12.000
3 11.999
4 11.998
Was the researcher precise in their measurements?
Assuming that the actual mass of the beaker was 12.000 g, was the researcher accurate?
Was there error associated with these data? If so, which type?

Answer 1

During the course of each experiment, the mass of beaker will fluctuate, due to thermal expansion and other factors, which accounts for some of the scatter. Imperfect experimental technique and roundoff error account for additional spread.

The distribution of measurements is 11.9995 ± 0.0015 mL, whereas the actual mass was only 12.000 g, which is outside the measured distribution.

This underlines that point that statistical analysis of your observations will not reveal systematic bias. Standard deviation is precisely defined and easy to calculate, but it is not equivalent to uncertainly, let alone error.