Which type of chart focuses on the relationships between activities in complex projects?

The type of chart that focuses on the relationships between activities in complex projects is the PERT flow chart. Program Evaluation Review Technique (PERT) flow charts are specifically designed to depict the interdependencies of tasks within a project, allowing project managers to visualize how different activities relate to one another in terms of sequencing and timing.

By showcasing the sequence of tasks and identifying the critical path, PERT charts provide insights into which activities must be completed before others can start, which is especially valuable in complex projects where timing and interactivity among tasks are crucial for successful outcomes. This allows leaders to effectively allocate resources, prioritize tasks, and understand potential bottlenecks, ultimately enhancing project management and delivery.

In contrast, while activity charts outline tasks, swimlane diagrams provide clarity on roles and responsibilities across processes, and milestone charts focus on key deliverables and timelines rather than the relationships between tasks. Each of these other options plays a unique role in project management, but none capture the intricacies of task interdependencies like the PERT flow chart does.