A negative percent error indicates that the measured or experimental value is less than the true or accepted value. In other words, it means that your result was an underestimate compared to the correct value.
To calculate percent error, you use the formula:
Percent Error = ((Measured Value – True Value) / True Value) × 100%
If the measured value is lower than the true value, the subtraction in the numerator will yield a negative number, resulting in a negative percent error. This is important because it helps in assessing the accuracy of measurements and understanding whether your results are above or below the actual value.
In practice, a negative percent error shows that improvements might be needed in the measurement process or that there might be systematic errors affecting the results.