How Are Precision and Accuracy Different?
To illustrate the difference between precision and accuracy, suppose that a tape measure is used to measure the circumference of two circles—one small and the other large. Suppose a result of 15 cm for the first circle and 201 cm for the second circle are obtained. The two measures are equally precise; both are measures to the nearest centimeter. However, their accuracy may be quite different. Suppose the measurements are both about 0.3 cm too small. The relative errors for these measures are 0.3 cm out of 15.3 cm (about 1.96 percent) and0.3 cm out of 201.3 cm (about 0.149 percent). The second measurement is more accurate because the error is smaller when compared with the actual measurement. Consequently, for any specific measuring tool, one can be equally precise with the measures. But accuracy is often greater with larger objects than with smaller ones. Confusion can arise when using these terms. The tools one uses affect both the precision and accuracy of one’s measurements. Measur
