Interesting, I had an idea there were studies from WWII aircraft plants or the like, but have never tried to look them up. The optimum must depend strongly on

Interesting, I had an idea there were studies from WWII aircraft plants or the like, but have never tried to look them up. The optimum must depend strongly on what work you are doing, how expensive tired mistakes are to fix, how much downtime there is waiting for someone else, etc.