Some jokes are jokes about themselves. They are called meta-jokes. “Meta-“ means above/about. These kinds of jokes are for very brainy people, like my son-in-law, who sent today’s cartoon to me.
The writer, Randall Munroe, is a super-geek and famous in high-tech circles. His online cartoons involve stick characters, which are simple to draw and let the reader focus on the language of the cartoon. He often writes about computers and math, but sometimes he does language jokes. If you are a math and science geek, you might like to start reading his work.
This cartoon is about the difference between causation and correlation, which are important concepts in science and technology.
What's So Funny?
If you don’t understand this joke, you are not alone. Many Americans don't understand it. Let me try my best explanation to this joke about a joke.
Correlation means that two things are related to each other.
Causation means that one thing caused another thing to happen.
Just because two things are related doesn't mean that one of them caused the other. It could be that they just happened in a similar way or at a similar time. Causation always involves correlation, but correlation doesn't always involve causation.
In this case, Person A tells Person B that he used to think related things had a cause/effect connection, but after taking a statistics class, he doesn't think that. She thinks the class caused his change of mind. He says it's possible, but he isn't sure.
The joke here is that they are talking about connections and causality. He says his change in belief is connected in time (before-after) with his statistics class. She thinks the class caused the change, but he is now more cautious about making such claims.
After this long explanation, you may still not think this cartoon is funny. Share this with your friends at work. If they think it's funny, then they will appreciate it when you share the XKCD website with them.