Guido Imbens

If you just look at the treatment received, you are back in the murky waters of confounded observational data.

This conundrum was elegantly solved by the Nobel Prize-winning framework developed by Angrist, Imbens, and Rubin.

They showed how to use the randomized assignment itself as an instrumental variable.

variable.Okay, let's walk through this carefully.

It only works if you swallow the pill.

Perfect.

To deploy the math, Angrist, Imbens, and Rubin conceptually divided the population into four latent strata based on how they respond to the instrument.

It was the four compliance groups.