Percentage error, Absolute error, Relative error

All measurements are not exact. Therefore, whenever we use measured or values or round off value. We introduce error into the figure. Example if Ajide is 1.6 tall to 1 d.p. then the actual height could be between 1.55m and 1.65m. the error can be calculated as 1.55 – 1.6 or 1.65 – 1.6 i.e -0.05 or + 0.05 i.e ±0.05

Absolute error: it is the difference between the measured value and the actual value.
Relative error: it is obtain by dividing the absolute error by the actual value

Example

1. The weight of a book is given as 1.1kg but the actual weight is 1.24 kg. What is the percentage error?

Solution

Error  =          1.24kg – 1.11kg = 0.14kg

2. Instead of expressing 2/21 as a decimal number to 2 s.f a student expressed it to 2 d.p. Find the percentage error.

Solution

2/21   = 0.095238 = 0.095   to 2 s.f, Error= 0.10 – 0.095 =  0.005