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Calculating LT50 (median lethal temperature, aka LD50) quickly in R

Say you’ve got a bunch of survival/mortality data from an experiment. Maybe you exposed batches of snails to various high temperatures for a few hours, and recorded the number alive and dead in each batch at the end. Now you’d like to report the median lethal temperature (or perhaps a lethal dosage if you were injecting stuff into critters). We can do this fairly quickly using R statistical software to perform a logistic regression and back-calculate the LT50.

This assumes that you already have R installed on your computer and you know how to fire it up.

To start with, we need … Continue Reading