The answer is: Validity
To put it simply, validity refers to whether the study is actually measures the things that the researchers intended to.
Validity in every studies is extremely depended on whether the variables that the researchers use actually have a correlation with the phenomenon they're observing with the study.
In the case above, Valencia wants to measure people's narcissism. Because of this, The questions that she asked to her subject is really correlating with the subject's narcissistic tendencies.
