THE CHINESE EYEGLASS EXPERIMENT. This paper, “The Unprincipled Randomization Principle in Economics and Medicine” by Stephen T. Ziliak and Edward R. Teather-Posadas describes an experiment by development economists in 2012. The experiment attempted to determine whether wearing corrective eyeglasses might help kids with poor eyesight to do better in school.
The experiment involved some 19,000 students with poor eyesight. About half of them were part of a “control group” that did not get eyeglasses nor any other eye care. You may be wondering about why the “gold standard” of a controlled randomized experiment was used, but this is part of mainstream thinking. (The sponsors of the experiment included the World Bank). Ziliak and Teather-Posadas say that a simpler experiment would have been for just one of the economists who wears glasses to take them off and try to read what’s on a blackboard (sample size of 1 rather than 19,000).