71  Variable Classes

I use the term variable class to refer to two broad types of variables:

Independent Dependent
Description Fixed parameters studied by the experimenter What you have measured. They change according to the state of the independent variables.
Example Genotypes, developmental stages, cell lines, growth conditions Expression levels, blood pressure, intensity, presence/absence of a substance
Typical axis \(x\) \(y\)

Not every plot will have an independent and a dependent variable. Many plots only contain one variable, or multiple dependent variables. Although the typical orientation is y as a function of x, in which case we plot the dependent variable on the y axis, the orientation may change in specific cases (see XX).