## Frequency Table

A frequency table lists all categorical values
along with their respective number of observation, i.e., `Frequency`
in the specified column.
While the frequency is the count of a particular categorical value,
the relative frequency is its percentage relative to the total
sample size, indicating how the qualitative data are distributed.

When the second variable of categorical values is specified, the paired observations of the first and the second variables are summarized in the form of contingency table.