Percentage error is a measurement of the discrepancy between an observed and a true, or accepted value. When measuring data, the result often varies from the true value. Error can arise due to many different reasons that are often related to human error, but can also be due to estimations and limitations of devices used in measurement. Regardless, in cases such as these, it can be valuable to calculate the percentage error. The computation of percentage error involves the use of the absolute error, which is simply the difference between the observed and the true value. The absolute error is then divided by the true value, resulting in the relative error, which is multiplied by 100 to obtain the percentage error. Refer to the equations below for clarification.
Steps to Calculate the Percent Error
- Subtract the true value from the observed value.
- Take the absolute value of step 1
- Divide that answer by the true value.
- Multiply that answer by 100 and add the % symbol to express the answer as a percentage.