Hybrid Systems: Combining Approaches

2009: Netflix Prize winner announced

BellKor's Pragmatic Chaos wins $1 million

Their solution: Not one perfect algorithm, but 107 different algorithms blended together

Each algorithm votes:

• Collaborative filtering: 0.82 confidence
• Content-based: 0.75 confidence
• Time trends: 0.68 confidence
• Recency bias: 0.71 confidence
• Device type patterns: 0.64 confidence

Final prediction: Weighted average of all votes

The lesson: Combining approaches beats perfecting one approach. This is called ensemble learning.