When troubleshooting coverage issues for a wireless network as it appears to new client associations,...

A passive survey is the most appropriate survey type when diagnosing coverage and signal strength issues. It listens to beacons and probe responses to map the RF environment, showing actual signal levels, noise levels, and AP visibility across the site. Passive surveys are particularly valuable for understanding how clients "see" the network when associating.

From CWDP-305:

“Passive surveys are used to validate RF coverage and detect interference. They listen to beacon and other management frames to determine AP coverage areas without needing to associate to a specific AP.”

Active surveys require client association and are more suited for performance-related assessments (like throughput and latency), while predictive surveys are used for pre-deployment modeling.

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on Post-Design ValidationandTroubleshooting