Can someone tell me what the independent variable is and why?

Cary is interested in studying the effects of alcohol on reaction time (the amount of time it takes a person to respond to a stimulus once he or she detects the presence of that stimulus). Accordingly, he gives half the subjects in his study 2 ounces of alcohol mixed with orange juice. He gives the other subjects a substance mixed with orange juice that tastes and smells like alcohol, but is non-alcoholic. Shortly afterwards, he exposes all the subjects to a situation in which they must press the space bar on a computer keyboard when they see a red light appear on the monitor. In this example, what is the independent variable?Can someone tell me what the independent variable is and why?
The independent variable is the amount of alcohol that Cary gives to a test subject. It is called the independent variable because it does not depend on anything other than Cary's judgment. Cary controls the value of the amount.



Incidentally, the dependent variable, which depends on the independent variable -- the amount of alcohol, would be the amount of time it takes a test subject to press the space bar after seeing the light come on. Cary has no direct control over how long it takes the person to press the key, only how much alcohol that person receives.Can someone tell me what the independent variable is and why?
The independent variable is the thing that the experimenter manipulates.



In this example, it is whether the participants get the alcohol or non-alcoholic substance mixed in with the orange juice.Can someone tell me what the independent variable is and why?
More generally, the independent variable is the thing whose value one actively controls and can change, while the dependent variable is the thing whose value then changes as a result.



In your example, the independent variable is the alcohol, and the dependent variable is the reaction time.

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