The document discusses techniques for establishing shorter feedback loops between developing features and measuring user behavior, including:
1) Shadow traffic which runs new and old features simultaneously to get early feedback without users noticing a difference.
2) Visual reports which assess the quality of a feature through a report (e.g. HTML page) of key metrics.
3) A/B testing which statistically compares user behavior between a control and test group after exposing each to a different variant of a feature. Sample size considerations and statistical significance are discussed.