Adding planned design to xp might help novices' productivity (or might not): two controlled experiments

Extreme Programming (XP) suggests using Evolutionary design, always implementing the simplest solution that satisfies the current iteration's requirements, instead of Planned (or Traditional) up-front design. Some developers have questioned the usefulness of Evolutionary approach's enabling practices (e.g., refactoring, test-driven development) arguing for the naturalness of, and need for, Planned design. Two controlled experiments were conducted to compare both approaches regarding product quality and programmer productivity. Results from both studies show that (1) there is no significant difference in the product quality, independently of experience, but (2) novices are more productive using the Planned approach.