Which one of the following statements is correct?
(A)There is no difference between precision and accuracy
(B)A good precision always means good accuracy
(C)Accuracy means that all measured values of an experiment
(D)A measurement may have good accuracy but poor precision
The correct answer is (D). The measurements for a given substance may be close to the known value, but if the measurements are far from each other, then we have accuracy without precision.
This means that although the measurements are correct as a group, each individual reading is a poor measure of the true value. This situation is said to have poor repeatability i.e., the measurements taken in succession don't agree well.
All other statements are incorrect.