Final answer:
The category of conflict not included by Thamhain and Wilemon in their study of project conflict is 'Personal'. They instead focused on technical and project management aspects such as technical issues, cost, and schedules.
Step-by-step explanation:
The category of conflict that is NOT included in the categories used by Thamhain and Wilemon in their study of project conflict is d) Personal. Thamhain and Wilemon identified several typical areas of project conflict, including goals, administrative procedures, technical aspects, cost, schedules, and performance criteria, but not personal or interpersonal conflict. The importance of understanding conflict categories lies in the ability to manage and resolve conflicts effectively within the project management environment. Identifying the correct category of conflict helps project managers in developing appropriate strategies for conflict resolution and maintaining a productive project team dynamic.