HELP in a test rn

Dr. Rodriquez is considering conducting a study examining whether narcissistic people have poorer romantic relationships than those who are not narcissistic. One of her first tasks is to determine which of her participants are narcissistic and which are not. She decides to use the scale created by a colleague, the Donal scale. Question 1 reads, "I tend not to think about other people as much as I think about myself." Question 2 reads, "I do not have a high opinion of myself." Question 3 reads, "I think other people think I am really special."

Before using the measure in her study, Dr. Rodriquez gives the measure to a group of participants on the first day of the semester and again on the last day of the semester. She then compares the scores between the two time points. This is a test of which of the following?