What is meant by "percent error"?


Quick Answer

Percentage error is the discrepancy between the actual, calculated or approximate result of a measurement and the expected or exact values. Percent error represents this value as a percent of the exact result.

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Full Answer

Percent error may occur due to approximation errors. For example, if an instrument used to make a measurement is inaccurate to a certain degree or cannot calculate to a certain decimal, then an approximate value close to the exact value might occur. More commonly, percent error occurs from calculations involving irrational numbers, such as pi.

Although pi is defined as an irrational number with infinite decimal digits, pi is often rounded to 3.14 to make calculations easier. The area of a circle when calculated with 3.14 is slightly larger than the area calculated with pi. Thus, the imprecision of percent error in making calculations can lead to faulty readings.

One can calculate percent error by subtracting the experimental result from the theoretical result, and then dividing the difference by the theoretical result and multiplying the quotient by 100. The closer this calculated amount is to zero, the closer the calculated result is to the expected value. A high percent error suggests an approximation error or some other underlying cause for the discrepancy.

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