To evaluate the effectiveness of a new song recommendation algorithm on Spotify, I would employ a combination of quantitative and qualitative metrics. Quantitative metrics may encompass: User Engagement : The effectiveness of the recommendation system would be closely linked to user engagement metrics, such as the number of songs played, total time spent on the platform, usage frequency, and skip rates. Higher engagement levels suggest that users are likely enjoying the recommended songs. Algorithm Accuracy : A rise in the number of recommended songs being added to playlists or saved in users' libraries can serve as a direct indicator of the algorithm's accuracy. As for qualitative metrics , conducting user surveys and interviews would provide valuable insights into user satisfaction. Additionally, tracking the 'churn rate' is crucial; if the new recommendation algorithm results in an increase in users leaving the platform, it may signal dissatisfaction with the new feature.