When scientists talk about "precision," they mean the reproducibility of an experimental result or measurement. If you are weighing a softball on a balance that measures in ounces, your results will lack precision because you will differently estimate half-ounces and quarter-ounces. If you weigh the softball on a digital kitchen scale that weighs in quarter-ounces, however, your results will have greater precision because you will not be estimating quarter-ounces. Relative average deviation is a way of expressing precision.

Write the individual results for which you want to calculate the relative average deviation. For example, write, "3, 7, 14."

Add all the results and divide by the total number of results using a calculator. For example, (3 + 7 + 14)/3 = 8." The mean of your data is 8.

Add the difference of each individual result and your answer. If the difference is negative, drop the negative sign. For example, (3 - 8) + (7 - 8) + (14 - 8) = 5 + 1 + 6 = 12.

Divide your answer by the sum of the mean of the data and the number of individual results. For example, 12/(8 x 3) = 0.5.

Multiply your answer by 100. For example, 100 x 0.5 = 50. The relative average deviation of your data is 50 percent.