Correlation between two variables can help us predict the causation between the two variables. However, correlation is not causation. Sometimes, the correlation between two variables can be due to a third variable. As we all know, it is easy to neglect the third variable, whereas the third variable plays a key role. Therefore, we should have scientific thinking when we meet correlation versus causation questions.

For example, most of high IQ students can achieve a great result in the exam. High IQ and high score is positive correlation, which means as IQ goes up, scores increases, too. However, can we conclude the factor to have a high score is high IQ? No. The third variable is diligent. Some students do not have a high IQ, but they read a lot of books and do a lot of exercise before exam in order to get a high score. In this case, if we conclude all high score students have high IQ, the result is against the scientific thinking. In reverse, we still use this case. Can we conclude that all high IQ students get a high score? No. Some high IQ students may be additive into Internet. Even though they are smart, yet they do not study. In this case, the third variable is that smart students do not focus on studying. Therefore, we cannot say high IQ causes high score or high score due to high IQ.

When I studied this concept, I came up with a question, which is "Is causation correlation?" I searched some information online, and I realized we could conclude that Causation is correlation. Causation happened when two things have a relationship with each other. Unlike the concept we stated above, there is not a third variable. Therefore, correlation is not causation. However, causation is correlation.

http://stats.org/in_depth/faq/causation_correlation.htm

This link of article helps me understand the difference between causation and correlation better.

This is a drawing illustrating the relationship between correlation and causation. It depicts a correlation between ice cream consumption and crime, but shows that the actual cause is temperature.

I like how you explained that correlation and correlation cannot always go in the same direction. I hadn't thought of it that way! :)