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Five readings of the length of a pencil are 17.6 cm, 17.4 cm, 17.7 cm, 17.5 cm and 17.3 cm…

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Five readings of the length of a pencil are $17.6\ \text{cm}$ , $17.4\ \text{cm}$ , $17.7\ \text{cm}$ , $17.5\ \text{cm}$ and $17.3\ \text{cm}$ . Find the mean, the mean absolute error and the percentage error, and write the result.

Need a reminder? The key ideaShow

For readings $a_1, \ldots, a_n$ : the best value is the mean $\bar{a}$ ; each absolute error is $|a_i - \bar{a}|$ ; their mean is the mean absolute error $\Delta\bar{a}$ .

\displaystyle \text{relative error} = \frac{\Delta \bar{a}}{\bar{a}}, \qquad \text{percentage error} = \frac{\Delta \bar{a}}{\bar{a}} \times 100\%

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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