Suppose an experiment is designed to test the durability of batteries in different conditions. all of the batteries tested are double-a (aa) brand x. all sets of batteries are preconditioned in different environmental conditions for exactly 168 hours (1 week).
set 1: 0°c (freezing point of water)
set 2: 24°c (approximately room temperature)
set 3: 37°c (approximately body temperature)
the batteries are then continuously used to power identical mechanical drummer toys. as long as the toy keeps drumming the battery is considered functional. the drumming time for each toy is measured as an indication of battery durability.
in this experiment, which condition is not controlled?
brand of batteries
type of battery (battery size)
temperature
test for durability