What Are Box Plots?

A box plot gives you a simple overview of five of the most important values in statistics: Minimum value, first quartile ( $Q_{1}$ ), median, third quartile ( $Q_{3}$ ) and maximum value. Between the first and third quartiles you draw a box. The opposite sides represent the quartiles. You draw a line through the middle of the box, representing the median. The length of the box is the interquartile range. You draw a line down from the bottom of the box to the minimum value and a line up from the top of the box to the maximum value. A box plot is therefore a visualization of the dispersion in the data.

Example 1

You are to make a box plot of the following data:

$\begin{array}{l} 1, 1, 2, 2, 2, 3, 3, 3, \\ 4, 4, 4, 5, 5, 6, 6, 6 \end{array}$

$1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6$

You will then need:

1.: minimum value $= 1$
2.: maximum value $= 6$
3.: median $= \frac{3 + 4}{2} = 3.5$
4.: $Q_{1} = 2$
5.: $Q_{3} = 5$

The box plot looks like this:

Boxplot from data

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What Are Line Charts?

How Histograms Work

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