Friday, July 24, 2015

Correlation does not imply Causation !

One of the fundamental tenets that any analytics newbie needs to learn is that - Correlation does not imply Causation !

Using statistical techniques, we might find a relationship between two events, but that does not mean that the occurrence of an event causes the other event. Jotting down a few amusing examples that I found from the internet.
  • The faster windmills are observed to rotate, the more wind is observed to be. Therefore wind is caused by the rotation of windmills 
  • Sleeping with one's shoes on is strongly correlated with waking up with a headache. Therefore, sleeping with one's shoes on causes headache.
  • As ice cream sales increase, the rate of drowning deaths increases sharply. Therefore, ice cream consumption causes drowning.
  • Since the 1950s, both the atmospheric CO2 level and obesity levels have increased sharply. Hence, atmospheric CO2 causes obesity.
  • The more firemen are sent to a fire, the more damage is done.
  • Children who get tutored get worse grades than children who do not get tutored
  • In the early elementary school years, astrological sign is correlated with IQ, but this correlation weakens with age and disappears by adulthood.
  • My dog is more likely to have an accident in the house if it’s very cold out.
A good site showcasing such spurious correlations is here - http://www.tylervigen.com/spurious-correlations