This recommendation provides the derivation procedure of contribution values that provides information about a relationship between quality-influencing factors (e.g., media quality levels and stalling) and the final media session quality score of adaptive audiovisual streaming services. More precisely, contribution values show how much each quality-influencing factor affects (i.e., decreases) the final media session quality score provided by a quality estimation model (e.g., P.1203 or P.1204) using Shapley theory, which is a key concept in cooperative game theory for distributing profits in a game among participants. This derivation procedure can be used to monitor the streaming service since operators can know which quality-influencing factors decrease the final media session quality score.