Im confused by correlation versus causation. If two things are correlated, cant they also have a cause-and-effect relationship?
Yes, they can, but correlation doesnt automatically mean causation. The trick is not to assume that a cause-and-effect relationship exists when it is only a correlation. Heres a simple example. You put your lucky coin in your pocket right before your psychology exam. You do really well on the test. Even if you dont believe in luck like this, you might be tempted to think the coin helped you along. Suppose the next exam, the same pattern happens. But then the final exam comes along and you forget your coin. Sure enough, you flunk! We would come up with a powerful positive correlation, but would it be cause-and-effect? No. In this case the worry that you felt when you noticed the coin was missing may be the causal agent. This would be a great example of positive correlation (coin-bearing behavior correlates positively with strong test performance) but is unlikely to be true causation.
