Final answer:
The experiment has flaws, including the potential Hawthorne effect, lack of control, and self-selection bias which could influence self-esteem changes beyond the frequency the professor calls on students.
Step-by-step explanation:
One significant flaw in the students' experimental design is the potential impact of the Hawthorne effect, which occurs when subjects change their behavior simply because they are aware that they are being observed as part of a study. This awareness could lead to changes in self-esteem unrelated to the frequency of being called upon by the professor. Another issue is the lack of control within the experiment. Without controlling for other variables that may influence self-esteem, such as the content of the questions or the quality of the students' responses, it is difficult to attribute changes in self-esteem solely to the frequency of being called upon. Additionally, changes in self-esteem are subjective and difficult to measure, potentially leading to self-selection bias, where the changes could also be due to the students' intrinsic motivation rather than the experimental manipulation.