[Solved] What is the injector driver output voltage used to actuate a Siemens HEUI? A) 115 volts DC. B) 12 volts DC. C) 12 volts AC. D) 48 volts DC. Hypothesized Mean Difference: The presumed difference between the means of two populations or conditions being compared in a statistical hypothesis test. Two-Tail: A term used in statistics referring to the two-tailed test of significance that checks for the possibility of positive or negative differences. Observations: The act of noting and recording something with instruments or the naked eye as part of a scientific or empirical study. Untreated Population: A group in a study or an experiment that does not receive the treatment or intervention being tested.