What is the Formula for Percent Deviation?

The word “percent deviation” is used in statistics and many scientific fields to indicate how inaccurate test results may be. You need a calculator and a reference standard to calculate percent deviation.

Compared to the norm, compare your data

You are frequently given a benchmark or a theoretical consequence to anticipate from your data in experiments or data-recording tasks. For instance, it is well known that the acceleration caused by gravity is 9.8 m/s2 in a physics lab that calculates the acceleration of a falling item.

However, your calculated result could not be 9.8 m/s2 precisely due to minute discrepancies in calculations of the distance or time to fall. Check how closely your outcome matches the benchmark after you’ve finished your calculations and experiment.

Find the distinction

By deducting the smaller of the two from the larger, you may determine the discrepancy between your calculation and the norm. If you discovered 9.5 m/s2, for instance, the calculation for the difference is 9.8 m/s2 – 9.5 m/s2 = 0.3 m/s2.

Do the % deviation calculation.

The percent deviation is calculated by multiplying your data by the standard deviation by 100 and then dividing the result by 100. (|data – standard|) 100 * / (standard) The formula is expressed as follows for the acceleration experiment: 100 * (9.8 – 9.5)/(9.8) = 100 * (0.3)/9.8 = 3.06%

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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