Example 2: random variables
one way you might have sorted these variables is whether they are based on counting (such as the number of languages spoken) or based on measuring (such as the length of a leaf).
random variables are classified into two main types: discrete and continuous.
 a discrete random variable is one that has possible values that are isolated points along the number line. often, discrete random variables involve counting.
 a continuous random variable is one that has possible values that form an entire interval along the number line. often, continuous random variables involve measuring.