ABSTRACT
So far, we have used the term accuracy to describe how close a measured value is to a true value, a quantity we can estimate but never know. Accuracy can be refined further into related concepts: bias, trueness, and accuracy. As an example, assume you have purchased a traceable stainless steel weight of 10.000 g to test the balances in your laboratory. The weight is sold with documentation that would certify it as 10.000 ± 0.001 g. The “± 0.001 g” is the tolerance or the range in which the measured weight will fall if your balance is operating properly and is used properly. Even though the weight is traceable, there is still a tolerance associated with it. As long as we know what that tolerance is, we can use the weight as intended. If we put the weight on the balance and obtain a weight of 9.999 g, the balance is acceptably accurate because the measured weight falls within the tolerance of the traceable weight, which is the best we can do with this particular balance.
