An attribute that is manipulated by the experimenter while other aspects of the study are held constant. The outcome, response or attribute that changes as a consequence of variation in the independent variable. The problem with experimental study - the control you get and gain may lose validity in the real world. They"re 2 means, but are they significantly different?) Use statistics and probability to rule out the findings were due to chance. Reliability (consistency) dismiss unreliable measures i. e. drastic, unrealistic changes between measurements. All living structures and form chance (usually but not always gradually) over long periods of time. Evolution is change over time in the frequency with which particular genes occur within a breeding species . It"s a species when breeding between two different ones do not create viable offspring. We"re most closely related to apes, not chimps! Fishes have midbrain too, we have hindbrains too.