Weight of supermarket employees

Association

Joint Probabilities
Attendance
Poor Satisfactory Above average Marginal
Underweight 0.0450 0.0900 0.0150 0.1500
Normal 0.0825 0.3025 0.1650 0.5500
Overweight 0.0500 0.1200 0.0300 0.2000
Obese 0.0300 0.0650 0.0050 0.1000
Marginal 0.1700 0.5400 0.2900 1.0000

Conditional probabilities

Use this diagram to explain the interpretation of association and why independence is important.

In the first example, absenteeism is associated with weight — employees with normal weight are less likely to be off work.

In the second example (select from the pop-up menu), performance is independent of weight — the conditional probabilities for performance are the same for each weight category.

The probabilities are artificial and are only used to illustrate the idea of independence.