A clinic records how long each of 20 patients spent with the doctor…

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 clinic records how long each of $20$ patients spent with the doctor. The times are $5, 10, 15, 20$ or $25$ minutes.

Time (minutes)	5	10	15	20	25
Patients	2	5	8	4	1

Use the shortcut method to find the mean, the variance and the standard deviation. Treat the $20$ patients as the whole group.

Need a reminder? The key ideaShow

$\sigma^2 = \dfrac{\sum f x^2}{N} - \bar{x}^2$ and $\sigma = \sqrt{\sigma^2}$ . For a sample, divide the sum of squared deviations by $n - 1$ to get $s^2$ .

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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