A university historically has a course completion rate of $61\%$. They pilot a peer-mentoring intervention with $250$ students and observe that $140$ students complete the course. Identify the variable of interest and classify its type.

The variable is the completion rate of the pilot group and it is an ordinal variable.

The variable is the time to completion in weeks and it is a quantitative discrete variable.

The variable is the students' GPA and it is a categorical nominal variable.

The variable is the completion indicator for each student (complete/not complete) and it is a categorical binary variable.