What type of test design technique is most effective for testing screen-dialog flows?

State transition testing is particularly effective for testing screen-dialog flows because it focuses on the transitions between different states of an application as users interact with it. In a screen-dialog flow, the user navigates from one screen or state to another based on various inputs, and the application reacts according to the defined rules for each transition. This technique helps to validate that the application responds correctly to user actions, ensuring that all possible state changes are tested.

By using state transition testing, testers can identify valid and invalid transitions and ensure that the application behaves as expected when transitioning from one screen/dialog to another. This is essential in ensuring the robustness of user interfaces, where different inputs can lead to varied application states.