# S1 - Please explain this example of a box plot and outlier

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Thread starter 4 years ago
#1
QUestion is this:

I am after help with part B.

I have worked out that Q1= 15, median = 16, Q3=16.5
I have worked out that a lower outlier must fall below 12.75 (none of the data pieces fall below 12.75, so there are no outliers there), and that the upper outliers must be above 18.75 (which there is one - 25 - which falls above 18.75)

I look at this example of the box plot for the question: (the mark scheme, they got the same values for the outliers and Q1, median and Q3)
Attachment 599616599624

I get that there are no lower outliers below 12.75, and the lowest value is 14, so the box plots most left point is 14. I get why the Q1 is placed at 15, Q2 at 16 and Q3 at 16.5 on the box plot too. I get that the outlier is placed at 25, because the outlier must be above 18.75 (and 25 is above 18.75, so is an outlier). However, I don't get why they would put the highest value at about 18.75.

The two highest values were 18 and 25, and we know that the value of 25 is an outlier, because anything above 18.75 is an outlier. So why is the highest value point plotted on the box plot at 18.75 and not 18? Can you explain this to me please? I don't get it.

Thank you so much
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