What type of usability testing is informal and ideal to quickly get feedback from users on small changes during any user-centered design phase?

Hallway testing is a type of informal usability testing that takes advantage of getting quick feedback from users who are not specifically involved in the design process. This method involves approaching individuals who happen to be passing by, often without prior arrangement, and asking them to interact with the product or prototypes. This approach is highly effective for gathering immediate feedback on small changes or features, as participants can provide their impressions and thoughts without the pressure of structured testing environments.

The essence of hallway testing lies in its simplicity and the speed with which data can be collected, making it particularly useful during the iterative phases of user-centered design. This method can highlight usability issues and areas for improvement before more formal testing phases take place.

Other options may not fully capture the informal nature and quick nature of feedback that hallway testing provides. Anonymous surveys often lack the interactive component of direct observation. Remote testing can be structured and less spontaneous. Unmoderated testing might still require a degree of setup and is not always as immediate or casual as hallway testing. Overall, hallway testing uniquely fulfills the need for quick, informal feedback in the design process.