Typo / inconsistency in chapter 1.5.1

[mornan]

In the chapter 1.5.1
"boxplot" is written as "box plot". Everywhere else it is written as "boxplot". This is somewhat inconsistent.
... se below
"To visualize the relationship between a numerical and a categorical variable we can use side-by-side box plots. A boxplot ... "

[nightcityblade]

Hi, I'd like to work on this. I'll submit a PR shortly.