Josh Witten

Your glass of sweet tea is half full

sweet tea @ maxine's on main in bastrop — Photo by nealpage (CC BY-NC 2.0)

Expectations are funny things. They can take the exact same experience and give it entirely different interpretations.

Why is having your half-empty glass of unsweet tea refilled with sweet tea so much worse than having a half-empty glass of sweet tea topped off with unsweet tea? Same drink. Different expectations.

The experience of half-sweet tea entirely depends on your expectations. In both situations, the quantitative experience is exactly the same. The qualitative experience is entirely different. Both are totally different.

Science Writers 2012

For the next several days (26-30 Oct), I will be back in the Triangle Area (Raleigh, North Carolina) pretending to be a science writer. I kind of hope nothing gets done around here while I’m gone – would make me feel needed.

V is for Correlation

Correlation is not causation.

Who hasn’t heard that old chestnut? No one. How many people actually disagree? No one. Who actually uses the phrase “old chestnut”? No one. See the theme? No one. Wait, what? Stupid pattern loving human brain. Where was I? Argh, stupid forgetful human brain. No one.

Deep breath. Start again. While no one may believe that correlation is the same as causation, it is a tired line that is frequently used, not as an incisive critique of analytical errors in analysis, but as a casual dismissal of potentially inconvenient results without any serious consideration. Casual dismissal requires some style, a touch of pithiness. I find the related aphorism to be more aurally attractive:

Correlation does not imply causation.

It has more words, but I think it is something about the rhythm that I like. The accuracy of this phrase is, however, up for debate. And, it is debated, usually in a rather uneducated manner. The debate centers around the word “imply”. In its original, more mathematical usage, “does not imply” essentially had the same meaning as “is not”. In modern, common usage (eg, internet comment sections and dictionaries), “imply” has a much broader meaning more along the lines of “suggest”. This underscores a major problem with distinguishing correlation and causation – we use the same language and tools to discuss them both. Continue reading “V is for Correlation”