Probit Analysis of bioassays: Sure, you are seriously talking about it
After reviewing a manuscript, I thought of talking to my friend who works in the prestigious Government institution to know as to how he estimates various parameters of toxicity like LC50, fiducial limits [FL] or Confidence intervals [CI], intercept. And this reminded me of my days as a M.Sc. student when I would do these calculations using a Facit® manual calculator on a tabulated sheet that our insect toxicology teacher, Dr. B.S. Atri would provide us. It was tedious work involving filling of columns like concentrations, log concentrations, % mortality, their transformation into probits, weighting coefficients, empirical probits, expected probits, working probits and other parameters meticulously up to three decimal points until we came to an equation, y=a+bx, where y is 5.0, a, an intercept and b, a slope and x (log LC50) is what we will calculate. For 95% FL, we used two equations, m1=m-1.96 √ V and m2=m+.6 √ V where m1, m2, lower and upper FLs of LC50, √ square root of varian