::: 3.10 Random Variables :::
In the previous section, we discussed probability models, and this carries into this section, as discrete and continuous random variables are specific types of probability models. A discrete random variable has a countable number of possible values, with the sum of all the probabilities being exactly 1. A probability histogram is a graphical interpretation of this concept. A continuous random variable takes all values on an interval. A density curve is the visual manifestation of the probability distribution of a continuous random variable.