A shop measures the lengths of 32 screws in a box. Find the mode.

Contributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A shop measures the lengths of $32$ screws in a box.

Length (mm)	Screws
0-5	15
5-10	10
10-15	5
15-20	2

Find the mode.

Need a reminder? The key ideaShow

The modal class has the greatest frequency. For equal class widths,

\displaystyle \text{mode} = l + \dfrac{f_1 - f_0}{2f_1 - f_0 - f_2} \times h,

where $f_0$ is the frequency before the modal class and $f_2$ the frequency after it. A missing neighbour has frequency $0$ . For inclusive classes use the boundaries.

The worked solution

Have you tried it?

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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