HCI Midterm 2 Review
Why should our prototype goals be automatically measurable?
Ideally, we got these from our falsifiable usability requirements, so we should be able to design user studies to prove based on the data that a prototype is sufficent
Where is polling often used?
In low-level programming (more so than high-level)
How many "chunks" of information are users generally able to remember?
7 plus or minus 2
Microsoft example of Pareto Law
By fixing the to 20% of reported bugs, 80% of the errors and crashes would be eliminated
What is Miller's Law of Short-Term Memory Load?
George Miller (Princeton) "Magic Number" (1956) Users are generally able to remember 7 +/- 2 "chunks" of information
Should you show failure with your system in a video prototype
Good idea (show success and failure)
What two states does a button have?
Hover state Click state
What's an example of Miller's law with an ipad?
Users will be able to remember about 7 plus or minus 2 gesture actions quickly (but do get better with more practice)
When are Storyboarding and Video prototypes used?
VERY early in the design process
What was the deal with Walter Teague's airplane prototype
Very big Wanted to perfect the airline experience Could be modified easily
What was the deal with Bill Verplank's star people?
Very rough sketch, helps you focus on the tasks
What is the Pareto Law?
Vilfredo Pareto: 80-20 rule (80% of the world's wealth owned by 20% of the population)
What is the Peak-End rule?
Humans judge their experiences on the peak of the experience (pleasant or unpleasant) and how it ended Net pleasantness and length of experience is disregarded
What is Polling?
"Is it pressed? Is it pressed? Is it pressed?..." A software design pattern in which a process *repeatedly* checks another entity for a status change Examples: - Keep pinging a server to make sure a connection stays alive - Every 10 ms, check the printer for readiness - In a game, check every frame whether the player is dead
Example of Pareto Law in HCI
"What should be fixed on our website?" two issues account for 50% of all comments
What is Events (as opposed to Polling)?
"Yo, lemme know when it's pressed..." A software design pattern in which a process *waits* patiently for an event to occur and only reacts when necessary Examples: - Server, tell me when you are ready to connect - Printer, let me know when you are ready to print - Game over screen waits to be notified that player is dead
How do you optimize your design with Fitts' Law in mind?
*Size*: Some thingy done more often? Make the button bigger. ^HOWEVER, you gotta be careful because this can harm the *consistency* of the interface *Distance*: things done more often should be closer to the avg position of the pointer ^HOWEVER, you gotta be careful because it may be faster to have a logic-based arrangement than a frequency-based arrangement b/c it'll minimize the time the user spends looking for things
What lessons about prototypes can you draw from the IDEO Digital Camera prototype? (thingy with interchangeable parts and faked stuff)
- Prototypes nearly ALWAYS incomplete - Goal is to SIMULATE specific aspects of the design and acquire knowledge regarding those targeted aspects - IDEO wanted to know more about the digital aspects of the camera
What are Krug's 3 Usability Laws?
1) Don't make me think 2) It doesn't matter how many times I click, as long as each click is a mindless, unambiguous choice 3) Get rid of half the words on each page, then get rid of half of what is left
Why do we prototype? (3 reasons)
1) Gain insights into user behavior 2) Communicate ideas to other teammates/stakeholders 3) Collect data for arguing the best design choice
What are the 3 benefits of storyboarding?
1) Holistic focus: helps emphasize how an interface accomplishes a task 2) Avoids early commitment 3) Helps get all stakeholders on the same page in terms of the goal
What are the seven usability laws?
1) Miller's law of short-term memory load (chunks) 2) Fitts' Law (targeting) 3) Keystroke Level Model (KLM) (additive) 4) Hick's Law (Decision time) 5) Power Law of Practice (yee) 6) Pareto and Zipf Laws (80-20) 7) Peak end rule
What are the components of an Event? (2)
1) The source of the event (which thing fired the event) 2) The event type
What are the 3 parts of the prototyping process?
1) What are your goals for you prototype? What do you wish to learn? 2) How can you measure if that goal has been achieved? How can you measure which of the prototypes is superior? 3) What is the MINIMUM amount of work necessary to produce, measure, and learn from your prototype?
Steps to make WOO prototype
1. Map out scenarios and application flow. 2. Put together interface "skeletons" 3. Develop "hooks" for wizard input. 4. Put it all together 5. Rehearse wizard role with a colleague.
Example of Pareto Law with cell phone bandwidth
10% of cell phone users use 90% of the bandwidth
What is the most common estimate in the difference in price in making a change before any code is written?
100 times cheaper [Jakob Nielsen]
What is the Keystroke Level Model (KLM)?
A model that provides numerical predictions of user performance. List out all the subtasks of a task (such as moving hands, clicking, etc) and sum the estimated times of these tasks (from the table) to get the total estimated time of the task
What is a high-fidelity prototype?
A prototype that mimics the design very closely, but remains functionally incomplete This might be actual code, or actual physical devices that don't work fully.
In Miller's Law, what is "chunking"?
A psychological phenomenon where individuals group responses when performing a memory task Like remembering 3453535635 as 34-53-53-56-35
What theoretical data type helps with modeling the complex interactions of a mouse with a button?
A state machine
How many categories can humans categorize stimuli, according to Miller?
About 7 (e.g. can categorize pitches into about 7 categories, and then get very quickly worse at the task after that)
How does the Pareto Law help in HCI?
Almost always a time-budget tradeoff when designing Pareto Law helps designers focus on the majority of issues with an interface quickly
Twenty years of usability engineering experience uniformly indicates that the biggest improvements in user experience come from gathering usability data when?
As early as possible in a design project
What is the relationship of cost of change and fidelity of prototype?
As prototypes become higher fidelity, they become more expensive to change
What are the benefits of video prototyping?
Cheap and fast Great communication tool (helps get everyone on same page, portable and self-explanatory) Can serve as a 'spec' for developers Ties interface design to tasks (aligns/orients interface choices; makes sure you have a complete interface)
What is Hick's Law?
Describes the time it takes for a person to make a decision based on the number of choices available Decision time increases quickly for small values for n choices, but then diminishing returns
What relationship was highlighted by the graph of time spent vs learned?
Diminishing returns
What do predictive models like Fitts' Law seek to accomplish?
Discover how well a user will use the system w/o actually testing with real users
Is wizard of oz high or low fidelity?
Either (can wizard of oz a paper prototype) However, remember that the more 'real' the wizard's mirage is, the more realistic the user's reactions will be
What did Antonio Damasio discover?
Emotions help us make decisions People with damaged prefrontal cortexes had trouble making decisions
True or false: Prototypes should be required to be complete
False
WOO advantages
Faster to make / cheaper, thus more iterative prototypes possible. • Creating multiple variations is usually very easy (no code to rewrite). • More "real" than pure paper prototyping or mockups. • Identifies bugs and problems with current design. • Places user at center of development. • Can envision challenging to build application. • Designers learn by playing wizard.
What are the different types of prototypes?
Feel: What does it look and feel like? Implementation: How does it work? Role: What is the experience like?
Is storyboarding high or low fidelity? Why?
Focused on tasks and flow of user interaction NOT focused on specific interface elements and how they look, etc. Thus it is incredibly low-fidelity.
Functionality vs. Time graph
Functionality goes up and wizarding goes down over time as the prototypes become higher fidelity?
What is the Zipf law?
George Kingsley Zipf Most frequent word appears about twice as much as the second most frequent In general, nth most frequent word occurs 2x more often than the (n+1)th most frequent
How do you get the constant b in Hick's Law?
It's empirically derived
What are *Known Unknowns*? What are *Unknown Unknowns*?
Known: Aspects of a design that you know you don't know and wish to learn • i.e., "Which color scheme is most user friendly?" Unknown: Aspects of a design that you don't know are open issues • i.e., "Why can't old people use this tiny screen!?"
What is the Power Law of Practice, intuitively?
Learning curve effect on performance
What is video prototyping?
Like a storyboard but a video product
How does the Zipf Law (linguistics) relate to HCI?
Most frequently used command in a piece of software used about twice as frequently as second most frequently used
Can Events be implemented with Polling?
No (that would be polling :p)
Is audio always necessary with video prototypes?
No, can have someone explain it live
Should you show specific interface elements in storyboarding?
No, just the tasks and flow of user's interaction
In prototyping, can you just make a bunch of prototypes that are various levels of awesome?
No--prototyping is about *defining questions* about your designs and building something that answers those questions
Does the button do anything other than throw events?
Nope! The other stuff is the job of the observer
How much time should you spend storyboarding?
Not much
Explain how the components of the Observer Design Pattern interact at a low level
Observable holds a map of event types to the observers that care about each event type Observer can be attached/registered to an event type Observer can be removed from a list (no longer cares so stop notifications) One observer can register for many observables, and vice versa
What are the caveats of Hick's ("Hick-Hymen"?) Law?
Only applies to groups that can be reasonably categorized e.g. would not apply to a list of random options, but would work for alphabetized options (user can search)
Video prototyping steps (probably dont need to know)
Outline/storyboard Obtain equipment Focus on MESSAGE, not production quality Film
What concept from 1st week is Fitts' Law an example of?
Predictive Model (predicts things w/o need for users)
What is important to remember with WOO prototypes?
Remember that you'll need to build actual software for wizard's role eventually, so it must be possible!
How does the Zipf law help in HCI?
Shows that generally you can design for the masses
What's a cool use of Fitts' Law on Macs? Why does this work?
Sides of the screen and corners are infinitely targetable, so the user can target these very quickly and easily
Drawbacks of WOO
Simulations may represent otherwise imperfect (or impossible) tech. • Wizards require training and can be inconsistent. • Playing the wizard can be exhausting ☹ • Some features are difficult (or impossible) to simulate perfectly. • May be inappropriate in some venues.
What is the Observer Design Pattern?
Software design pattern in which the object, called the *subject*, maintains a list of its dependents, called *observers*, and notifies them automatically of any state changes, usually by calling on one of their methods Button tells the observer when to act
What concept was highlighted by the graph of number of prototypes over time?
Start out with lots of low fidelity ones, and narrow down to a few higher fidelity ones
What was Apple's big prototype with their stores?
Stores sorted by type of activity (simulated in warehouses)
How do you perform the minimal work possible with a prototype?
Strip out every feature that is not absolutely necessary
Storyboarding is all about...
Tasks!
What is the Power Law of Practice mathematically?
The *log* of the reaction time for a particular task decreases linearly with the *log* of the number of practice trials taken (Practice makes perfect, but with diminishing returns)
What do you put in a video prototype?
The WHOLE task including motivation and success Draw on tasks you observe Illustrate important tasks your system enables Can help scope a minimum viable product. Changes what design teams argue about (in a good way)
What was Floryan's Wizard of Oz prototype?
The learning software with the frustrated cartoon character (found that matching the student's emotions worked best)
What tasks/scenarios should you focus on with storyboarding?
The most common ones
What is prototyping?
The rapid creation of an approximation to a design idea for the purpose of retrieving feedback and knowlegde
What should storyboards convey? (3)
The setting (people involved, environment, tasks) The sequence (Steps involved, what leads someone to need to use your app, tasks) Satisfaction (What motivates people to use the system? What does it accomplish? What need does it fill?)
Fitts' Law eqn
The time is roughly logarithmic to the distance divided by the size
What is Fitts' Law?
The time it takes to reach a target with a pointing device is a function of its size and distance from current pointer position
Example of Pareto Law with taxes
The top 20% of U.S, taxpayers pay 68% of all taxes
How do you define your prototyping goals?
choose a subset of usability requirements that we wish to test with a given prototype
When should you Wizard of Oz a prototype?
There is an advanced technology in your system that you don't have time to build / incorporate into prototype. • Speech recognition, artificial intelligence, etc. You haven't determined how best to implement a feature (e.g., personalized feedback) and want to test it first. When it's faster/cheaper/easier than making a real thing
T or F: The general rule is that you should progress from low to high fidelity slowly as the design process continues.
True
T or F: prototypes should be easy to change
True
True or false: having lots of prototypes is good
True
T or F: bad drawing is good in Storyboarding. Why?
True Helps you focus on the *task* and not on imagery
What determines the fidelity of a video prototype
Typically where you are in the design process
Where does the log_2 in Hick's Law come from?
Users quickly categorize and halve the number of choices iteratively until they select what they want ("not quite, but it's ok to think about it this way")
What was the deal with Jeff Hawkin's Block of Wood?
Wanted to learn about the form factor and the experience of living with the Palm Pilot 24/7 Did NOT learn about things like battery life, sound effects, feedback, etc. So your prototype can literally be a block of wood
What is a Wizard of Oz prototype?
Where a human operator simulates the complex interactions of the prototype so they don't have to be implemented to test
What is a digital mockup?
Where the software is simulated digitally (e.g. build.me)
Are fancy high-fidelity videos ok?
Yes!
Is code ok for a high-fidelity prototype?
Yes, but still not designing the whole system
What does it mean that prototypes should be "disposable"?
You should be mentally prepared to dispose of them (not designing the system itself, just a prototype)
What 3 things are usability engineers concerned with?
• Developing products that elicit positive responses such as feeling at ease, enjoying the experience, etc. • Eliciting specific types of emotions such as motivation to learn, be creative, play, be meta-cognitive, etc. • Eliciting trust (e.g., making users feel comfortable with divulging their payment info).
Benefits to paper prototypes
• Very fast evaluation and testing of an interface! • Very Cheap! Less resource consuming. • Easy to change and adapt • Estimated to be 100 times cheaper if NO code is written. • Can be used to collect important usability information! • User involvement at an early stage • Encourages creativity (not limited by coding skills) • Can be used as subset of system documentation (e.g., hand to engineers and say "build this")
