A researcher is investigating the effects of caffeine consumption on student writing performance. Because the researcher will evaluate both the speed of assignment completion and the number of grammatical errors, she will need to include more than one variable in her study

The answer is dependent variable.

Explanation:

In experimental research, an independent variable is predicted to affect one or more dependent variables. In this example, the caffeine intake is expected to change the participants' writing speed and/or accuracy. This means the experiment includes two dependent variables.

An easy way to remember the difference is to say: independent causes change in dependent.

answer; reactive is your answer; good luck