Reading Box Plots

Box Plots/Box and Whiskers

It is another way to represent data.  We have already used Dot Plots and Histograms to represent data.  Box Plots are an easy way to show if a number is above the middle of data or below the middle of data.

5 Number Summary

We use the 5 number Summary (5 special data number) to create and help interpret data from a box plot.  The 5 number summary includes:  Minimum, Maximum, (Q1) Quartile 1 or Lower Quartile, (Q2) Median, and (Q3) Quartile or Upper Quartile.

Parts of a Box Plot

• Min – Minimum: Smallest number of the Data Set

• Q1 – Lower Quartile:  The median of the lower half of the data

• Q2 – Median:   Middle number of the set of data

• Q3 – Upper Quartile:  The median of the upper half of the data

• Max – Maximum:  Largest number in the data set

• Interquartile Range (IQR): Q3 – Q1

Fill in the Blanks

What is the minimum (smallest number) of this Box Plot?

Fill in the Blanks

What is the maximum (largest number) of this Box Plot?

Fill in the Blanks

What is the lower quartile (Q1) of this Box Plot?

Multiple Choice

What is the Median (Q2) of this Box Plot?

• 80

• 82

• 81.5

Fill in the Blanks

What is the Upper Quartile (Q3) of this Box Plot?

Multiple Choice

Find the Interquartile Range (range of the "box") for this Box Plot. (Hint: Q3 - Q1)

• 92 - 77 = 15

• 77 - 92 = -15

• 92 + 77 = 169

• 92 - 77 = 25

Quartiles

• Quartiles divide the data set into four equal parts.

• 25% each

Median

• Divides the data set into two halves

• 50% of the data numbers are below this number

• 50% of the data numbers are above this number

Fill in the Blanks

Given the Box Plot: Identify the Minimum

Fill in the Blanks

Given the Box Plot: Identify the Maximum

Multiple Choice

Given the Box Plot: Identify the Lower Quartile.

• 33.5

• 33

• 34

• 34.5

Fill in the Blanks

Given the Box Plot: Identify the Median.

Fill in the Blanks

Given the Box Plot: Identify the Upper Quartile.

Fill in the Blanks

Given the Box Plot: Find the Interquartile Range. (Q3 - Q1 = 75.5 - 33.5)