Mendelian randomisation

How do you know whether smoking causes lung cancer? You could sample smokers and non-smokers, and look for correlations. Yet famously, correlation is not causation! Consider coffee drinking. Early on in studies of lung cancer, people sfound a correlation between coffee drinking and lung cancer. But this simply reflected the statistic that coffee drinkers are more likely to smoke. One could imgaine that carrying a lighter is correlates with lung cancer too.

Correlations could also be spurious: it depends on who you're sampling!

Why we need better methods

How do you know whether smoking causes cancer? A simple approach would be to sample a group of people to look for correlations. Yet famously, correlation is not causation, and even worse, it could be spurious.

Facetiously, what