Correlation and Causation: Third Factor and Directionality Problem

Discussion Assignment #13
1. Explain what the following statement means: “Correlation not causation”. In other words, why can't you prove causation with correlational studies?
Correlation not causation" means that you cannot assume that a causal relationship exists between two variables just because they are correlated. Correlation only indicates that a relationship exists between two variables; it does not indicate what kind of relationship exists.
2. What is the “third factor” problem concerning correlational studies as it relates to inferring causation?
The "third factor" problem is that a third variable may be responsible for the relationship between the two variables, rather than the two variables themselves. In this situation, it would be incorrect to infer a causal relationship between the first two variables from the data. For example, let's say that we observe a positive correlation between the amount of time spent studyin...