Final answer:
The dependent variable in Dr. Whoever's study is the test scores while the independent variables are the ambient noise level and the test difficulty. Lurking variables would need to be controlled to ensure that any observed differences in test scores are due to the manipulated variables.
Step-by-step explanation:
Dr. Whoever was interested in the effect of ambient noise level and test difficulty on test scores, which is an exploration within the field of psychology. In the described study, the dependent variable (DV) is the test scores. The independent variables, or manipulated variables, that Dr. Whoever is controlling are the ambient noise level (set to either "loud" or "soft") and the test difficulty (categorized as either easy or difficult). Each of these can affect the DV, which in this case, is the subjects' test grade.
It's important to control for lurking variables when trying to establish a causal relationship. Lurking variables, like previous coursework or societal encouragement in different fields of study, could explain differences in test scores that are not related to the variables being manipulated in the study. A well-designed experiment will control these lurking variables to ensure the validity of the conclusion drawn about the relationship between the independent variables and the dependent variable.