\begin{block}{Continuous variables}
When a numerical variable can have any numerical value on some interval it is referred to as \textbf{continuous}. Only numerical variables can be continuous.
\end{block}

\begin{block}{Discrete variables}
If variables are not continuous they are referred to as \textbf{discrete}. All categorical variables are discrete and some numerical variables.
\end{block}

\begin{block}{Exploratory and response variables}
For every subject, the value of an \textbf{explanatory variable} influences the value that its \textbf{response variable} will obtain. A response variable can be influenced by several explanatory variables.
\end{block}