A sample obtained from the National Bureau of Standards had a calibrated weight of 20,000 g.

Question

When a student measured the weight three times with a balance the results were: 19,603 g, 19,599 g, and 19,600 g. What conclusions may be drawn regarding the accuracy and precision of the balance used by the student?

Answer 1

Precision is how close the different values are to each other and accuracy is how close the measured values are to the real value. Without doing any math or statistics, it appears that the precision of the balance is pretty good since all measured values are close to each other (19,603 vs. 19,599 vs. 19,600). However, the balance is not very accurate since these values are not very close to the real value of 20,000.

This is a general statement, and one should find the mean and S.D. and percent error, etc. and do a statistical analysis to draw a firm conclusion.