A Galton board with selection on significance

For a while now I’ve wanted to modify a physical Galton board to show selection on significance. I was never able to get around to it, so instead I made a virtual version.

Below is a normal Galton board where balls fall from the top and each peg gives a 50% chance of going left or right (p(right)=0.5). What makes this board unique is the Selection on Significance slider, which controls the probability that non-significant results fall out of the bottom of the board. You can also switch Significance Test between two-tailed and one-tailed (right) cutoffs.

You can explore how different levels and forms of selection on significance change the distribution. This little toy does not illustrate all of the issues related to selection on significance, but I think it is a nice intuition pump.

I expect I’ll use this in my teaching, and I hope other people find it useful too.