Float concepts in CPM: Which of the following statements about total float, free float, independent float, and interfering float are correct?

Introduction / Context:
Float (slack) quantifies schedule flexibility. Proper use of float helps level resources and absorb uncertainties without delaying project completion. Different float types serve different management purposes.

Given Data / Assumptions:

• Total float TF = LS − ES = LF − EF.
• Free float FF = min(ES of successors) − EF.
• Independent float IF = max(0, ES of activity − LF of predecessor − duration).
• Interfering float = TF − FF.

Concept / Approach:
Total float measures how much an activity may move without affecting project finish; free float preserves successors; independent float is the portion independent of both predecessors and successors; interfering float is the portion that, if used, will delay the early start of successors but not the project finish.

Step-by-Step Solution:
Confirm total float via ES/LS or EF/LF relations.Compute free float using successor earliest starts.Compute independent float using predecessor latest finishes and own ES.Find interfering float as the difference: TF − FF.

Verification / Alternative check:
Network calculations should show TF ≥ FF ≥ 0 and IF ≥ 0 (by definition floored at zero). Critical activities have TF = FF = IF = 0.

Why Other Options Are Wrong:
All listed statements align with standard CPM definitions; therefore 'All the above' is correct.

Common Pitfalls:
Using free float where preserving successor early start is not required; double-counting float when multiple successors exist; forgetting that independent float can be zero even when total float is positive.

Final Answer:
All the above.