Boxplot - Minimum number of observations

I am wondering how Matlab could plot a box-plot having both the box and the whiskers with a minimum of three observations.

Could someone please help me understand how it is possible to provide a five-number summary by using only three observations? Any published reference on this issue would be greatly appreciated.

Kind Regards,

Berk

Answer 1

[the cyclist]

You can define quantiles even with just two data points:

http://mathworld.wolfram.com/Quantile.html

That's not to say that it is statistically meaningful, but where does one draw the line on software deciding for you when to create what you ask it to created?

The exact description of what MATLAB does is well documented:

http://www.mathworks.com/help/stats/boxplot.html