Modified Box-Plot (ST370)
The box's ends are the quartiles Q1 and Q3 (use
formula in Lapin book to obtain the quartiles).
We draw the median inside the box.
If a point is more than 1.5*IQR from an end of the box, it is
an outlier. You draw the outliers individually.
Finally, extend whiskers out to the farthest points
that are
not outliers (i.e. within 1.5*IQR of the quartiles.
The function bplot in Slab will give you slightly different
boxplot from the modified boxplot explained above.
The end of the whiskers are the 10th and 90th percentiles.
However, the function boxplot in Slab will use
the same rule as above, though the quartiles are not
calculated using the formula you have in Lapin book. That is
the reason why I want you to draw by hand the modified boxplot,
to avoid any confusion. Different softwares do slightly different
things, the most important thing is always to understand what
you are doing and why.
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