Research has shown that better-looking people earn more money (Hamermesh, 2011). Does this mean that getting cosmetic surgery to improve appearance will result in a higher salary? A non-expiremental study on this issue found that having cosmetic surgery was associated with slight salary increases (Lee & Ryu, 2012).

Question: should we recommend that people get cosmetic surgery if they want to make more money?

What are other factors that could influence both the choice to get cosmetic surgery and salary? (Spurious relations)

Can the causal arrow also go the other way? (Reverse causality)