The document discusses various inputs that are considered when estimating activity durations for projects in the Certificate IV Project Management qualification. These inputs include enterprise environmental factors like historical duration databases, organisational process assets such as previous project results and records, the project scope statement including constraints and assumptions, the activity list and attributes, resource requirements and calendars, the project management plan including risk registers and cost estimates, and activity cost estimates if already completed. All of these inputs are analyzed and considered when producing estimates of activity durations for the schedule.