Which best describes accuracy

Accuracy describes how well a measuring instrument determines the variable it is measuring. How close the value is to real value. The level of accuracy of measuring tool determines the detail to which it can measure. In order to be accurate in their work scientists need first select a measuring instrument that allows an appropriate measure of accuracy and then to calibrate it. Calibrating an instrument involves measuring already known quantities to check how accurately it is. In the laboratory accuracy of a test is determined when possible comparing results from the test in question with results geenrated from an established reference method.