Dataset: tribol_tox.dat

Source: P.S. Hewlett(1969). "The Toxicity to Tribolium Castaneum
(Herbst) (Coleoptora, Tenebrionidae) of Mixtures of Pyrethrins
and Piperonyl Butoxide: Fitting a Mathematical Model,"
Journal of Stored Products Research, Vol. 5, Issue 1, pp1-9.

Description: Results of experiments varying pyrethrin and piperonyl
butoxide concentrations on mortality of beetles (tribolium castaneum).
Model fit (did not include control (0,0) in fit):

Y* = a + b1*log(pyrethrin) + b2*(pip_but)/(b3+pip_but)

Y* = 5 + z(Mortality proportion)    ("centerd" probit)

Variables/Columns
pyrethrin concentration   4-8
piperonyl butoxide concentration  10-16
number beetles exposed     20-24
number mortalities    28-32