0
$\begingroup$

I want to draw a boxplot with whiskers where a lower bound is equal to $Q1 - 1.5 IQR$ and an upper bound is equal to $Q3 + 1.5 IQR$, where $Q1$ is a lower quantile, $Q3$ is an upper quantile and $IQR$ ia an interquantile range.

My observations are positive, but the value $Q1 - 1.5 IQR$ is below $0$. My question is:

Where should I put a lower bound of whiskers on a boxplot: in the point $Q1 - 1.5 IQR$ (which is negative) or in the point equal to $0$, because all my observations are positive?

$\endgroup$
  • $\begingroup$ What do you by mean lower bound? The $ 1.5 \times IQR$ is a rule of thumb to highlight potential outliers. $\endgroup$ – Karl Oct 30 '18 at 13:50
  • 1
    $\begingroup$ I suggest using the lowest data value if none are outliers. $\endgroup$ – Karl Oct 30 '18 at 13:53
1
$\begingroup$

The whiskers should extend to the most extreme data points satisfying the criterion that they lie within $Q1-1.5IQR$ and $Q3+1.5IQR$ from the respective box edges.

e.g. see here and read about 'range'

$\endgroup$
  • $\begingroup$ Thank you for your response. $\endgroup$ – MathMen Oct 30 '18 at 14:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.