I do know there are some rules about boxes and whiskers to determine the skewness in a boxplot, but I am confused with some rules in this particular case:
Keeping in mind the rules, in this boxplot the median falls to the right of the center of the box, thus its distribution is negatively skewed. But I also can see that the right line is larger than the left line, thus "according to the rules" the distribution is positively skewed. How do I know the real skewness. Thanks in advance.
Best Answer
If you have access to the underlying data you could/should estimate the skewness according to some measure, a common measure being based on the third moment of the data, see here. Note though there are other measures and they won't necessarily give the same results.
Regarding the box plot itself, it is a crude summary of a distribution and not necessarily good enough to allow the skewness to be estimated. Indeed, there can be quite different data sets, with quite different skewness, that will have the same boxplot.