October 3, 2025

What Is Percent Error

Q: Can percent error be negative?

No, percent error is always expressed as a positive value. The formula uses the absolute value of the difference to measure the magnitude of the error, regardless of whether the experimental value was higher or lower than the accepted value.

Q: What is the difference between percent error and percent difference?

Percent error compares an experimental value to a known, true value. Percent difference is used to compare two different experimental values to each other when no true value is known.

Q: What is considered an acceptable percent error?

An acceptable percent error depends on the context of the experiment. In a high school lab, an error under 5% might be considered good, while in professional analytical fields, the required accuracy might demand an error of less than 0.1%.

Q: How does percent error relate to accuracy and precision?

Percent error is a direct quantitative measure of accuracy, which is how close a measurement is to the correct value. Precision, on the other hand, refers to how close multiple measurements are to each other, which isn't measured by percent error.

Learn how to calculate percent error, a crucial measure of accuracy in scientific experiments. Understand the formula and see practical examples.

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Defining Percent Error

Percent error is a calculation used in science to express the difference between an experimental value and a known or accepted value. It is a measure of how accurate an experimental result is, represented as a percentage of the accepted value.

The Percent Error Formula

The formula to calculate percent error is: Percent Error = [|Accepted Value - Experimental Value| / Accepted Value] × 100%. The vertical bars indicate the absolute value, meaning the result is always positive. The 'Accepted Value' is the true or theoretical value, while the 'Experimental Value' is the value measured in an experiment.

A Practical Example

Imagine a student measures the acceleration due to gravity and gets a result of 9.5 m/s². The accepted value is 9.8 m/s². The percent error would be calculated as: [|9.8 - 9.5| / 9.8] × 100% = (0.3 / 9.8) × 100% ≈ 3.06%. This means the student's measurement was 3.06% off from the accepted value.

Why is Percent Error Important?

Calculating percent error is essential for evaluating the validity of an experiment. It provides a standardized way to assess the accuracy of measurements and the precision of the experimental method. A low percent error indicates that the experimental results are close to the true value, suggesting a high degree of accuracy.

Frequently Asked Questions

Can percent error be negative?

What is the difference between percent error and percent difference?

What is considered an acceptable percent error?

How does percent error relate to accuracy and precision?