Final answer:
Mr. Coby's hypothesis about students' test scores would be an Independent variable, as it is the variable he intends to manipulate to observe its effect on the responding variable, which are the test scores.
Step-by-step explanation:
Mr. Coby's hypothesis about students' test scores can be categorized as an Independent variable. A hypothesis typically proposes a relationship where one variable potentially influences another. In an experimental study, an independent variable is what the researcher manipulates or controls to examine its effect on the dependent variable, which is the outcome being measured. Meanwhile, a responding variable (or dependent variable) is the one observed and expected to change as a result of the independent variable's manipulation.
In essence, the independent variable is the proposed cause, while the dependent variable is the observed effect. If Mr. Coby is hypothesizing that a specific factor, such as study time or teaching method, affects students' test scores, then that factor is the independent variable because it is what he would manipulate in an experiment to observe the effect on test scores, the dependent variable.