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.

i believe the answer is:   psychological  experiment

in this experiment, wilhelm wundt became the first person that implement scientific method in analyzing the pyschological phenomenon.

due to this result, wilhelm wundt also able to make psychology to be acknowledged as a separate scientific field from biology.

jupiter is mainly composed of hydrogen and helium just like a star. spectral analysis of jupiter has revealed that in addition to hydrogen and helium, the planet is made of water, methane and ammonia. those elements are in trace amounts. the core of the planet is thought to contain some rock and metallic hydrogen. i hope this will give you the answer to your question! : d