According to my experiments, the Energizer maintained its voltage (dependent variable) for approximately a 3% longer period of time (independent variable) than Duracell in a low current drain device. For a medium drain device, the Energizer maintained its voltage for approximately 10% longer than Duracell. For a high drain device, the Energizer maintained its voltage for approximately 29% longer than Duracell. Basically, the Energizer performs with increasing superiority, the higher the current drain of the device.
The heavy-duty non-alkaline batteries do not maintain their voltage as long as either alkaline battery at any level of current drain.
My hypothesis was that Energizer would last the longest in all of the devices tested. My results do support my hypothesis.
I think the tests I did went smoothly and I had no problems, except for the fact that the batteries recover some of their voltage if they are not running in something. Therefore, I had to take the measurements quickly.
An interesting future study might involve testing the batteries at different temperatures to simulate actual usage in very cold or very hot conditions.