The best estimate of the distance is the average or mean of the results of the three drivers. The precision of this number is a measure of how close any driver could expect to come to 22.3 miles, driving his own car. We write it this way, rather than as 22.3 1.3, because the precision tells us that distances measured by various drivers will reproduce to no better than 1.3 miles. A more sophisticated way to report the precision in a measurement is to use the standard deviation . The error in a measured result is the difference between the measured value and the true value of the quantity being measured.
Error indicates the accuracy of the measured value.
Error is to accuracy what precision is to reproducibility. An extension of the example above shows the meanings of these terms clearly. An accurate road survey gives the distance between Spags and Uno as 23.9 miles. The negative sign indicates that the measured value is smaller than the true value. The uncertainty in a measured number carries into calculations made using the number.