Anscombe Quartet
There are sequences A , B , C and D , about which the following is known:
| A | B | C | D | |
|---|---|---|---|---|
| Average x | 9.00 | 9.00 | 9.00 | 9.00 |
| Variance x | 10.00 | 10.00 | 10.00 | 10.00 |
| Average y | 7.50 | 7.50 | 7.50 | 7.50 |
| Variance y | 3.75 | 3.75 | 3.75 | 3.75 |
| Correlation between x and y | 0.82 | 0.82 | 0.82 | 0.82 |
| Direct linear regression | y = 3 + 0.5 x | y = 3 + 0.5 x | y = 3 + 0.5 x | y = 3 + 0.5 x |

Such is the oil painting. You can download .XLS with data for self-study.
The British statistician F.J. came up with this thing. Anscombe, and it’s called the Anscombe Quartet. Everyone has heard the saying about the average temperature in the hospital, and now you have a good illustration for it.
About the Anscombe quartet on the English Wikipedia.
UPD: the porting of this article to the Russian Wikipedia has begun , and they correctly notice that the author should be called Francis Enscomb .