Toxicity of cypermethrin to months Heliothis virescens
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Collett (1991) reports the results of an experiment 
on the toxicity of the tobacco budworm Heliothis virescens 
to doses of the pyrethoid trans-cypermethin to which 
the moths were beginning to show resistance. 
Batches of 20 moths of each sex were exposed for 3 days 
to the pyretoid and the number in each batch which were dead 
or knocked down was recorded. 
We fit a logistic regression model using log2(dose)
since the doses are powers of two.