A value stated with more precision than is actually possible, given the accuracy of the values from which it has been calculated. For example, if a three-metre length is cut off the top of a sixteen-metre tree, then, if the lengths had been quoted to the nearest metre, it would be spurious precision to describe this as being a reduction by 18.75%. The true percentage lies between 100 × 2.516.5 ≈ 15% and 100 × 3.515.5 ≈ 23%. A reasonable precision in this case would be one significant figure in the percentage: 20%.
Subjects: Probability and Statistics.