Using frequency tables to understand discrete variables

For an overview of discrete variables, you use frequency tables and charts. A frequency table can show the following:

• The values
• The count of the values, or the absolute frequency
• The proportion of the value, or the absolute percentage
• The cumulative frequency
• The cumulative percent
• Plus, you can create a bar chart or a histogram of the values' absolute percentage

Minimally, you need to calculate the counts of the distinct values of the variable.

Let me start with calculating the frequencies with T-SQL. Window aggregate functions are very handy here. The following query is a very efficient one. If you look at the first part of the query, you'll notice that there is a common table expression (CTE) query that calculates the absolute numbers, or the counts. The cumulative values—...