Human-Computer Interaction Module 2.1 Flashcards
__________ is about creating effective user interfaces (UIs)
Usability
________ strongly affects how software is perceived.
Usability
___________ is the means by which the software presents itself to the world.
The User Interface
What are the most important factors US adults consider when purchasing a new technology product according to a Harris Poll?
Ease of Use (61%), Customer Service (58%), and no Hassle Installation (57%)
This was a radiation therapy machine for treating cancer patients. It had an electron beam with two settings: a low-energy mode, beamed directly onto the patient, and a high-energy mode in which the beam was blocked by an X-ray generating filter. Tragically, the system’s design had a race condition between the user interface and the beam controller. If the operator chose a mode, and the machine started configuring itself, and then the operator backed up and made a different choice within the 8-second interval it took for the machine to swing its magnets into place, then part of the system wouldn’t receive the new setting. As a result, a fast, experienced operator could inadvertently give severe overdoses, and several patients died.
Therac-25 Radiation Therapy Machine
In 1988, the USS Vincennes guided missile cruiser shot down an Iranian airliner over the Persian Gulf with almost 300 people aboard. There were two failures in this incident. The radar operator interpreted the airliner as an F-14, descending as if to attack, rather than (in reality) a civilian plane that was climbing after takeoff. Both failures seemed to be caused by user interface. The IFF system was reporting the signal from an F14 on the ground at an airport hundreds of miles away, not the signal from the airliner; and the plane’s altitude readout showed only its current altitude, not the direction of change in altitude, leaving to the operator the mental comparison and calculation to determine whether the altitude was going up or down.
Aegis Radar System in USS Vincennes
An oil spill was caused by a helm lever on an oil tanker. The lever had three positions: Autopilot – Manual – Disconnected. In a tight passage off English coast, trying to maneuver in a narrow channel with fishing boats, the captain accidentally pushed the lever too far – past Manual to Disconnected. Since the supertanker turned very slowly anyway, the crew didn’t realize at first that they weren’t turning at all (feedback). Even then, they had so many other hypotheses for why the helm wasn’t responding (burned-out fuse, interconnect problem, etc.) that they didn’t think of the lever. The tanker hit the rocks, and a large oil spill resulted.
Supertanker Accident Off England
In April 2006, an Predator unmanned aerial vehicle (UAV) crashed while patrolling the US border in Arizona. The pilot (who fortunately was safely in a control room hundreds of miles away) reported that his primary control console “locked up”, leading him to switch over to a backup console – but before switching between the two consoles, it’s necessary for the user to match the control positions on the new console to those on the original console. The backup console was set to the fuel cutoff position (in other words, NO FUEL) when he did the switch over. As a result, the fuel was cut off to the UAV, and it went right down.
Predator UAV Accident
Usability has several dimensions:
- learnability
- efficiency
- error rate/severity
- subjective satisfaction
The difference between UI and UX through the iPhone explanation.
The iPhone at the left has a UI. What you see on its screen is part of its UI; it also has UI in other modalities than seeing and pointing (e.g., microphone, speaker, camera, tilt and shake sensing). But surrounding that single device and its UI is a constellation of products and services and experiences that constitute the entire iPhone experience. The packaging. (YouTube videos of people unboxing their phones!) The App store. The Genius Bar. The advertising. The calling plan you buy and the wireless reception you get and whether your friends have iPhones too. It’s all part of your experience with the iPhone, and user experience design aims to encompass all of it.
