Statistics often make us believe wrong conclusion and misled us into believing silly correlations.
Let me tell you a story that happened in Country Blue Chips (CBC).

A freshly minted assistant professor (in statistics) “discovered” that drinking orange+apple juice makes you smarter. He runs a regression analysis after a grant by the largest manufacturer of juices in CBC. He then engages 10,000 pupils from CBC primary school, and split them into groups of 10 comprising of 1,000 pupils per group.

Each group is given different compositions of orange and apple juice. E.g., group 1 drinks 10% orange juice+90% apple juice; group 2 drinks 15% orange juice+ 85% apple juice and so on. If the professor can have a large enough sample, he can have an unlimited number of sample groups. He then realized that hey, drinking orange juice and apple juice daily for 1 year does not increase the entrance score of the local gifted programme for 9 groups of pupils. However, coincidentally, the last group that drank 15.5% orange and 84.5% apple juice actually had a 99% percentage of people entering the gifted stream. “Okay, I am going to use this statistic and write a paper on it! Based on a 99% confidence interval, the hypothesis that orange+apple juice can make your child smarter is true! 99% went into gifted stream after drinking the juice composition!” Read more...