The purpose of program-level student learning assessment is to find where students are struggling and succeeding and make adjustments on the basis of those findings. The "loop" indicates that this is a continuous process of identifying outcomes, assessing learning, using this learning to improve curriculum or resources, and then once again identify outcomes.
Closing the loop is the part of assessment where the department gets to take action, where it gets to innovate and advocate for resources, where it truly "manages student learning." Based on the department's findings of where students are struggling or succeeding, the department can decide how to adjust curriculum or resources.
For example:
Maybe the department finds that students in the capstone course are having trouble writing at a level of mastery expected of them, as evidenced by their final capstone paper. Perhaps they need more practice writing earlier in the program, so the department decides to make all earlier courses writing-intensive.
Maybe the department analyzes key assessments and finds that students' quantitative reasoning in the advanced courses is not at the level of mastery expected. Perhaps they need additional tutoring throughout the major, so the department advocates for resources to build in tutoring workshops throughout the curriculum.
Maybe the department finds through an analysis of e-portfolios that students are not able to reflect on and learn from their own creative work at the level expected of them. Perhaps they need more guidance in the reflective process, so the department encourages faculty to introduce reflective exercises throughout the introductory courses.
Departmental Curriculum Committees can be excellent homes for program-level assessment activities, as they are able to directly link assessment findings to curricular changes.