Using bivariate and multivariate descriptive statistics

In this section, we briefly talk about bivariate descriptive statistics. Bivariate descriptive statistics apply two variables rather than one. We are going to focus on correlation for continuous variables and cross-tabulation for categorical variables.

Covariance

The word covariance is often incorrectly used as correlation. However, there are a number of fundamental differences. Covariance usually measures the joint variability of two variables, while correlation focuses more on the strength of variability. Correlation coefficients have several definitions in different use cases. The most common descriptive statistic is the Pearson correlation coefficient. We will also be using it to describe the covariance of two variables. The correlation coefficient for variables x and y from a population is defined as follows:

Let's first examine the expression's sign. The coefficient becomes positive...