(Investigator 11, 1990 March)

Walking under a ladder is supposed to be unlucky.

The photo [here omitted] shows a courageous skeptic free of the superstitious fear of going under a ladder. A year after this picture was taken he was still alive and unable to point to any bad consequences of his experience.

A scientific test would be to:

1. Get a large number (say 1,000) of volunteers.
2. Randomly divide the volunteers into two groups.
3. Get all the individuals of one group to walk, one at a time, under a ladder.
4.Get all persons of the other group to walk one at a time under something else – a bridge or a tree.
5.For both groups keep a careful record of casualties.
6.Use a statistical test (for example the Chi-square test) to calculate if the casualty rate of the two groups differed significantly.
7.In case the bad luck influence of ladders has a delayed effect the two groups should be reassessed for casualty rates at regular (perhaps yearly) intervals.  

As far as I know such a scientific investigation of unlucky influences of walking under ladders has not been done. There is no reason to think that walking under a ladder is any more unlucky than walking under a bridge. So why waste time with a scientific test when we are reasonably sure of the result?