In an experiment to test the effects of alcohol on memory, the experimenter gives vodka mixed in orange juice to one group of subjects and orange juice with no vodka to the other group. She then measures the memory skills of both groups by means of a memory test. In this study, the independent variable would be

a. the presence or absence of vodka in the orange juice
b. intelligence
c. scores on the memory test
d. a placebo

A. The presence or absence of vodka in the orange juice

Explanation:

This test is been called the memory test in which it would be grouped in different groups and can take a little time which starts from five minutes till as much as it can last. Here, some skills like memory are the first to go when we're tired. This test assesses your ability to remember how long ago something happened to your memory. If you're tired you won't be as good at remembering when you saw or did something. This is a timed memory test designed to test your ability to quickly store and recall small items of everyday information. It's not easy and very few people have a memory agile enough to score over 80%. The memory test will take under five minutes.

i am confused, what is the question? i can you out if you put it into more depth.

you answered your own : -/