A [[random variable]] is a function that maps events from the sample space to the real numbers. The term "random variable" is a legacy term; random variables are neither random nor a variable. By convention, a random variable is denoted by a capital letter near the end of the alphabet (e.g., $X$, $Y$), whereas the specific instances of the random variable is denoted by the corresponding lower case letter. In statistics, we will model populations using random variables. Features or [[parameter|parameters]] of these random variables (e.g., mean, variance) will tell us about the population we're studying. A random variable is discrete if the set of possible values (or support) is discrete, continuous if otherwise. Multiple random variables can be mapped to the same sample space (e.g., the number of customers entering a store every hour and the time between any two customers entering the store can both be derived from observations of customers entering a store). ```dataview TABLE WHERE up = this.file.link ```