I'm just starting to use box & whisker plots
and have a (possibly very naive) question
about using them with skewed distributions.
The box represents skew in the middle of the
distribution nicely by showing the quartile
locations q1, q2, and q3. But the whisker
lengths are defined in terms of IQR=q3-q1, so
the whiskers are the same length for both tails.
This means that the skew in the tails (i.e.
below q1 or above q3) is not represented,
as far as I can see.
I wonder why the same value of IQR is used
to calculate the whiskers at both ends of the distribution.
Instead, I'd think the whisker should be longer on the side
with the longer tail. It would be easy enough to
define the whisker lengths for the two tails
separately, for example in terms of 2*(q2-q1)
and 2*(q3-q2). I'm just wondering why that
isn't routinely done. Have I overlooked
something obvious?
Thanks for your comments,
(By the way, with the distributions I am examining,
it would be very unhelpful to transform the scores
to eliminate the skew, since the skew itself is part
of what's interesting about the dataset.)
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