Boxplot

I’ve used these quite often, but I never got to understand theoretically.

Well, I thought each is just represented by the quantiles, there are 4 quartiles.

So actually, it really doesn’t work that way, because there are outliers. I got this wrong on the quiz, so it is time to learn.

Basically, the upper and lower need to be caculated, here is a summary $\text{5-number summary}:(\min ,Q_1,\text{median},Q_3,\max )$ $\text{Lower Outlier Boundary}=Q_1-1.5IQR$ $\text{Upper Outlier Boundary}=Q_3+1.5IQR$ $IQR=Q_3-Q_1$