Wikijunior:The Book of Estimation/Errors

Do you still remember that in measurements, there is no way of getting the exact value? Since our measurements are never accurate, there must be a difference between our measurements and the exact, unobtainable value. That's why we have error. In this chapter, we will learn how to calculate different kinds of error. Sometimes, we will assume that we know the exact value. Other times, we will try to figure out the largest possible error that will appear.

Before you start

Skim through the chapters before this one except estimation in calculation. Make sure you understand everything in there. Also, take a look at this problem. Remember it – we will be using it for the rest of the chapter!

Example I
Question	Joe Bloggs is measuring a block of flats. It takes the shape of a cuboid. It is ten storeys high and the first storey is around three metres tall, the others about the same. The length the building is around six metres, and the width four metres. All these measurements were done with a tape measure, where the distance from any two successive markings is 1cm. How accurate and precise are the measurements? How much might the measurements differ from the actual ones?
Solution	Read on to find out!

Table of contents

• Absolute error
• Maximum absolute error
• Accumulated error
• Relative error
• Percentage error