While a relationship between two variables may be observed, it is not enough to say that there is a casual relationship whereby one variable causes a change in the other.
- A study of primary school children found a high positive correlation between shoe size and reading ability. Thus there is a physical cause for some students’ reading problems. Alternative explanation: Age is a stronger factor. Older children tend to have larger feet and more time to learn how to read.
- A study of health care numbers found a high positive correlation between the number of doctors in a city and the number of sick people. It is concluded that we should have fewer doctors. Alternative explanation: larger population gives rise to a greater number of sick people, and hence more doctors to tend to them.
Want to suggest an edit? Have some questions? General comments? Let us know how we can make this resource more useful to you.