Performance and weight of high school children
Association
Athletic performance | ||||
---|---|---|---|---|
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, athletic performance is associated with weight — children with normal weight are better athletes.
In the second example (select from the pop-up menu), maths 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.