Forum Discussion
Excel Box and Whiskers
I made a graph "Bow and Whiskers" with 5 values: (see bitmap at the end of this message)
Min = 32,5
Q1 = 37
Q2 = 39
Q3 = 40
max = 43
(and choose for the option inclusive median)
A nice box with 2 wiskers appears in a diagram where the vertikal axis give me values from 30 to 44
When I dminish te minimum value lower than 32,5 !! then the the whisker under the box disappear and a point appears instead ...
Why is the whisker disappearing?
How can I get with the minimum value equal for example to 32 the missing whisker (without changing the option inclusive median)?
I want to get the next result:
- A graphic box and TWO wiskers whith the values
Min = 32
Q1 = 37
Q2 = 39
Q3 = 40
max = 43
Why is the second whisker dissapearing?
Is there a word around or update for this problem (without changing the values for Q1, Q2, Q3 and max?
Thanks
Erwin
9 Replies
Hello ErwinVanLoo,
Box and whisker plots are designed such that data points that are outliers are plotted outside of the "whisker". An outlier is considered to be a data point that is 1.5 times the interquartile above the third quartile or below the first quartile. The interquartile range for this data set is Q3-Q1 or 40-37=3. To determine the range for outliers, that would be:
- Q1-(1.5*3)=37-4.5=32.5
- Q3+(1.5*3)=40+4.5=44.5
So, values below 32.5 and above 44.5 will be plotted outside of the "whiskers". In your data set, since 37 is the lowest data point (and not an outlier), it become the lower "whisker".
I hope this makes sense!
Hello,
Thanks for your reaction, now I understand the reason why Whiskers suddenly appears / disappears.
It's a pitty that the behaviour of the Whiskers is not (well) documented.
Above all it is not the normal behaviour that can be expected from a specific whisker nor from the box and whiskers.
The given reason is not the way we expect that whiskers behave or should behave.
Is it possible to show always the wiskers and not to replace a whisker by a point if the distance is big?
We always need to draw the whiskers in statistical problems, that's why I made one document to have the different graphs (bar graphs, histograms, boxplot...) and in each boxplot I need one box and 2 whiskers.
Is it possible to make changes to the software so that the box and 2 whiskers will always be fully displayed?
Greetings
Erwin
Hello ErwinVanLoo,
If Q1 is equal to the lowest (non-outlier) value of a data set, this will become the lower whisker. Similarly, if Q3 is equal to the highest (non-outlier) value of a data set, this will become the upper whisker. There is no way to change this in excel.
I hope this helps!
