Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

Monthly Update sign up
Mailing List signup
Learning Math Home
Session 2, Part C: Precision and Accuracy
Session 2 Part A Part B Part C Homework
measurement Site Map
Session 2 Materials:

Session 2, Part C:
Precision and Accuracy

In This Part: Measuring With Precision | Accuracy vs. Precision

In everyday language, we use the terms accuracy and precision interchangeably. In mathematical terminology, however, the accuracy of a measure (an approximate number) is defined as the ratio of the size of the maximum possible error to the size of the number.

This ratio is called the relative error. We express the accuracy as a percent, by converting the relative error to a decimal and subtracting it from 1 (and writing the resulting decimal as a percent). The smaller the relative error, the more accurate the measure.

This interactive activity illustrates how it works. We can measure the length and the weight of two different items: a notepad and a desk. Although we measure each one to the same level of precision, the relative error differs because of the size of the object. Note 13

This activity requires the Flash plug-in, which you can download for free from Macromedia's Web site. A non-interactive version of this activity is also available.

Take it Further

Problem C5


Calculate the relative error for the measurement you made on the isosceles right triangle with side 3, and then one or two others.


Next > Homework

Learning Math Home | Measurement Home | Glossary | Map | ©

Session 2: Index | Notes | Solutions | Video


© Annenberg Foundation 2017. All rights reserved. Legal Policy