Statistics Tip of the Week: Always plot the data first; statistics alone can be misleading.

​It has been said that the first three laws of statistics are:

1. Plot the data.
2. Plot the data.
3. Plot the data.

(Some say, 1. Draw a picture, 2 Draw a picture. 3 Draw a picture.)

Statistics alone can be misleading.

The human mind did not evolve to understand concepts by reading words and numbers on a page. It is much more visual. Pictures can help give us an intuitive understanding that words and numbers cannot.
​
Here's an example. We're trying to determine if there is Correlation between the x and y values for either of the two Samples of data pictured below. 

​We calculate a Statistic for each Sample, r, the Correlation Coefficient. The value of r for these two plots are almost identical – and in both cases, it indicates a very strong Linear Correlation.
​
That makes sense for the one on the left. However, the one on the right is not linear at all. That data would more likely to be approximated by a polynomial curve.