CHOOSING THE RIGHT LAB MICE FOR AN EXPERIMENT. I posted here in 2009 about Richard Feynman’s lecture on how to eliminate possible alternative explanations in a controlled experiment. Feynman described how an experimenter named Young was trying to train rats to open the third door on a corridor. Young painted the doors carefully to make sure the textures of the doors were the same; he applied chemicals after each run so that the smell of food couldn’t influence the rats; he put his corridor on sand so that the sound in the corridor could not influence the rats. Feynman said that “from a scientific standpoint, that is an A-number-one experiment”.
The Economist (December 24, 2016) had an article about all the things that are done to make lab mice suitable for experiments. One pitfall to be avoided: in an experiment, mice that are litter mates and mice that are raised separately will respond differently. Another pitfall that is surprising is that in pain studies, mice can that are handled by men can experience much higher levels of stress than mice who are handled by women.
Because factors that are not known to be relevant, such as the gender of the person doing the lab work, can turn out to be important, copious notes are now taken to document the experiment.