A great example to show power of visualizing data: Anscombe’s Quartet Table


Let’s look at four datasets which have identical statistical properties:
Here’s the DATA:

ansombe quarter data visualizeHere’s their statistical properties:

Property Value
Mean of x in each case 9 (exact)
Variance of x in each case 11 (exact)
Mean of y in each case 7.50 (to 2 decimal places)
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

They look identical – don’t they? BUT let’s visualize the data:

Anscombe quarter data visualizationOnly visualizing data made it possible for us to understand and appreciate the “difference” between data-sets. Looking at just statistical properties made them appear “similar” – moral of the story: Visualize data! Graph data along with investigating statistical properties.

Source: Anscombe’s quartet

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