QUARTILES AND BOX AND WHISKER PLOTS
Ungrouped Data
The following are jump heights (in cm) from thirteen different cats. Describe the distribution of the data
using the median and interquartile range. 72, 40, 95, 58, 62, 35, 56, 65, 74, 68, 90, 40, 61
Median
Use the MEDIAN formula:
=MEDIAN(range)
Quartiles and Interquartile Range
Use the QUARTILE.EXC formula:
=QUARTILE.EXC(range,quartile)
Subtract to find the Interquartile Range (IQR).
Recall: You can format the number of decimal places displayed in a particular cell. Under the Home
Menu choose the drop-down menu under Number and choose the appropriate format.
Grouped Data
The following is a table of the time spent by a sample of men on household work.
Median and Quartiles
There is no formula in Excel to calculate the median or quartiles for grouped data.
Therefore we need to determine the total number of data points using the =SUM() formula then decide
which interval contains the median and which contain the 1st and 3rd quartiles.
BOX AND WHISKER PLOTS
Recall: When you make a histogram, always draw a box and whisker plot to accompany it
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There is no easy way to draw a box and whisker plot
on Excel
First use Excel to do all necessary calculations and
graphs (intervals, frequency chart, histogram,
quartiles and IQR)
Copy and paste the work from Excel into Word.
Under the INSERT MENU in Word choose SHAPES
Create a rectangle under the histogram to match the
IQR. Right click on the rectangle and you will get a
pop-up menu where you can adjust the fill, outline and
other features of your selected shape.
Create a vertical bar for the median
Create horizontal lines for the whiskers
To link the box and whisker plot together as one unit, hold the shift key down and use your mouse to
click each part of your plot. Then right click and select group.
100 data points
Min
Q1
Median
Q3
Max
IQR
2.5
12.5
17.5
22.5
37.5
10