Studies of college students have revealed that students with an locus of control tend to perform better academically than students on the other end of the spectrum. these better students most likely associate their academic success with

Internal; hard work

Explanation:

Locus of control refers to the degree to which people believe that they have control over their own lives. A locus of control is characterized as internal if the person believes that they can control their own life or external if they believe that life is controlled by outside factors which they cannot influence. In this example, college students with an internal locus of control did better academically, and were also more likely to associate their academic success with hard work.