What improvement tool would you use to gather data to confirm the reasons for the complaints about the HIM department?

Imagine you are the supervisor of the health information management (HIM) department in a large outpatient clinic. This department manages patient information and codes encounters for billing purposes. Complaints about your department are becoming more frequent and intense than in the past. Some clinic employees have complained that the HIM department takes too long to retrieve patient information that is not computerized. Others have expressed dismay over the rudeness of HIM staff. You decide to talk about these problems with employees throughout the clinic.
The clinic’s receptionists respond to you defensively. They tell you that the HIM staff won’t answer the phone and that they want some backup when they are busy with patients. You talk to the HIM staff and find their stories are just as negative. They say they are being charged with more responsibilities but have no additional help. They also complain that the receptionists transfer calls that they should be handling. The clinic’s billing staff are also upset with the HIM staff; they claim the department does not help them resolve insurance denials, causing payment delays. The clinic’s physicians say they cannot assume additional tasks to alleviate the situation because their days are already chaotic.