Why simple statistics can be so very misleading

Anscombe’s quartet was mentioned in a discussion on the Political Methodology listserv, as to what journalists need to know to stop looking like idiots when they report on social science research:

Counter to your intuition, all four sets of data have the exact same descriptive and bivariate statistics:

Property Value
Mean of x in each case 9 (exact)
Sample variance of x in each case 11 (exact)
Mean of y in each case 7.50 (to 2 decimal places)
Sample variance of y in each case 4.122 or 4.127 (to 3 decimal places)
Correlation between x and y in each case 0.816 (to 3 decimal places)
Linear regression line in each case y = 3.00 + 0.500x (to 2 and 3 decimal places, respectively)

Source: Wikipedia