Box Plots

The website below provides a good interactive to help you understand how to read and construct box plots.  There are also some questions to test your understanding of box plots
Interactive tool

Constructing a Box Plot Interactive

Guide to Constructing Box Plots

Constructing a Box Plot:

STEP 1: Order numbers from least to greatest.

Draw a number line that covers the range of the data.

STEP 2: Find the 5-number summary

STEP 3: Draw the box so that it includes the quartile values. 

     

STEP 4: Draw a vertical line through the box at the median value. 

STEP 5: Extend the whiskers from each quartile to the extreme data points.

*Don't forget to title your plot!

Vocabulary

The median (middle quartile) marks the mid-point of the data and is shown by the line that divides the box into two parts. Half the scores are greater than or equal to this value and half are less.

Inter-quartile range:

The middle “box” represents the middle 50% of data. The range of data from lower to upper quartile is referred to as the inter-quartile range. The middle 50% of data fall within the inter-quartile range.

Upper quartile:

Seventy-five percent of the data fall below the upper quartile.

Lower quartile:

Twenty-five percent of data fall below the lower quartile.

Whiskers:

The upper and lower whiskers represent data outside the middle 50%. Whiskers often (but not always) stretch over a wider range of data than the middle quartile groups.