The bubble-bursting, causality-revealing awesomeness of randomized controlled trials

A drawing shows a hand, labeled RCT, pulling threads with labels like income, environment, resources, education and quality of life.

Randomized controlled trials provide rigorous tests of the effectiveness of social interventions.


September 26, 2022

Countless lives have been helped or saved with the scientific evidence provided by an experimental approach three economists unleashed more than 20 years ago. Their innovation gave rise to a scientific movement that is clearly illuminating causality — how one thing directly causes another — within the intricate chaos of human behavior and society.


What are the most efficient ways to change the world for the better? What actions will effectively reduce poverty and illness, minimize violent crime or strengthen community resilience to extreme weather? Many governments and philanthropic organizations in the U.S. and abroad grapple with those tough questions when deciding how best to use the limited resources entrusted to them by taxpayers or donors.

Answering such complex questions requires clearly seeing something that is all too often hidden or murky: causality. Did a particular policy or initiative actually cause the desired effect? Or was it just a coincidence?

In the 1990s, a small group of researchers developed a scientifically rigorous way to design complex social experiments that can clearly distinguish those all-important causes from mere correlations and coincidences. Their method recast a statistical technique traditionally used in clinical medical trials, giving rise to a new movement in social science research and winning them a Nobel Prize.

Continue reading in Science Matters.

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