Recap: Interview• Structured
• Pre-determined questions to ask in a set way
• Semi-structured
• Start with set topics for discussion and follow up based on the
answers
• Useful for gathering requirements and understanding users’
opinions
Recap: Use Interviews to find out• Current behavior patterns • Opinions of currently used products/services • Complaints about poor or missing functionality • Comparisons of two or more known options
- What they do - How they do things - Their opinions about their current activities - Their complaints about their current activities - How much they like one thing that they know compared with
another thing that they know
But before all of these, you should have a clear definition of who “they” are!
Recap: Create interview questions1. Know what you want answered: Write down a problem statement
2. Reframe your problem statements: think of different perspectives to express the
same problem statements.
3. Build a list of questions based on your reframed problem statements
4. Paraphrase each question 2–3 times
5. Give the whole list of questions a structure
1) Introduction
2) Warm up questions
3) Main body questions
4) Wrap up
Recap: Guidelines for surveys1. Identify the scale and the significance of the unit
• Use the most intuitive order
• You can use positive or negative scales or a combination
2. Use odd numbers when you want to allow neutral responses
3. Use even numbers when you want to force a choice: positive or
negative
4. Provide a not applicable (N/A) when appropriate
5. Do not use too many degrees within the scale; seven is considered a
general limit
6. Test your questionnaires before use
Recap: Questionnaire & SurveyTypes of survey questions • Mutually exclusive choices (radio buttons)
• Non-mutually exclusive choice (checkboxes)
• Ranges (overlapping, open-ended)
• Scales (Likert scales, semantic differential
scales)
• Short answer fill-ins
• Comments
Likert Scale Example
Recap: Interview or Survey?Interviews • Explore a domain • Probe & follow-up • Capture multiple data sources • Rapport-building à Can ask
about sensitive issues But: • Expensive • Requires coding to interpret data • Difficult to make comparisons
Surveys • Defined sample from larger
population ➔ Generalizable • Comparatively low cost • Ask multiple questions efficiently • Standardized data allows
comparisons • Quantitative results
But poor for: • Starting research • Determining questions to ask • Clarifying questions for respondent • Following up unexpected comments
.
I'm fat because my metabolism is slow, hormone and gland
problems and too much stress. Health professionals should help
me lose weight. I am most worried about difficulties getting
to work.
Obesity is due to eating too much and not enough
exercise. The patient is to blame, so solutions must start with the patient. The biggest
concern is diabetes.
“The models people have of themselves, others, the environment and the
things with which they interact. People form mental models through
experience, training and instruction”
• An explanation of someone's thought process about how something
works in the real world
• Enable people to reason about a system
• Affect the way we see and interpret reality
• When users approach an unfamiliar system, they subconsciously refer
to their mental model, User’s model
“To break a mental model is harder than splitting the atom.”
--Albert Einstein
Mental models
User vs. designer model
the conceptual model of the system to be built
the way the user interprets the System Image
Gulfs of Execution & Evaluation The gaps between the user and the interface, pointing to how to better design an interface so that the user can cope with it • Gulf of execution: the distance between the user's goals and the
means of achieving them through the system
• Gulf of evaluation: the amount of effort required to determine the system state
The Model Human Processor
• Published by Card, Moran & Newell, 1983, in the book “The
Psychology of Human-Computer Interaction”
• Consider humans as information processing systems
• Core cognitive aspects • Attention
• Perception and recognition
• Memory
• Reading, speaking, and listening
• Problem-solving, planning, reasoning and decision-making, learning
• Describes how a user interacts with a computer system
Why model human performance?
• To predict impact of new technology/interface
• Apply model to predict effectiveness
• We could build a simulator to evaluate user interface designs
Human performance modeling
(1) Perceptual processor
Physical store from our senses: sight, sound, touch,… • Code directly based on sense used • Visual, audio, haptic, … features Selective • Spatial • Pre-attentive: color, direction… Decay time for working memory: 200ms
Pre-attentive • A limited set of visual properties that are detected very rapidly and
accurately by the low-level visual system
• Typically, tasks that can be performed on large multi-element displays
in less than 200 to 250 milliseconds are considered pre-attentive.
How many 3’s?
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How many 3’s?
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How many 3’s?
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Visual pop-out: shape (curvature)
Resources from : https://www.csc2.ncsu.edu/faculty/healey/PP/index.html
Change blindness A perceptual phenomenon that occurs when a change in a visual
stimulus is introduced and the observer does not notice it
Our visual intelligence can only detect changes in those parts of the
image to which we explicitly attend.
Selective attention The act of focusing on a particular object for a period of time while
simultaneously ignoring irrelevant information that is also occurring
This occurs on a daily basis and can be seen in basically any of your
interactions. Because it is impossible to give attention to every
stimulus in our environment, we use selective attention to select what
stimuli are important as events occur.
The problem with the classic ‘7±2’ • George Miller’s theory of how much information people can remember
• People’s immediate memory capacity is very limited
• The number of objects an average human can hold in working memory
(short-term) is 7 ±2
• Example: DECIBMGMC vs. DEC IBM GMC 6174591765 vs. 617‐459‐1765
The problem with the classic ‘7±2’ • Wrong application of ‘7 ± 2’ theory: Designers present only 7 options/
menus/icons/tabs. Why?
• People can scan lists of bullets, tabs, menu items till they see the
one they want
• They don’t have to recall them from memory having only briefly
heard or see them
• ‘7 ± 2’ applies to serial presentation of information
Recognition over recall • Recall – information reproduced from memory
• Recognition
– Presentation of information provides cues that information has been
encountered before
– Easier because of cues (context) for retrieval
Motor processor Receive input from the cognitive processor
Execute motor programs
• Pianist: up to 16 finger movements per second
Fitts’s law • Fitts’s law predict the amount of time taken to move to and select a
target
• It is faster to hit larger targets close to you than smaller targets
further from you
T = a + blog (D / S +1) - a, b = constants (empirically derived)
- D = distance
- S = size
• T increases as the distance to the target increases
• T decreases as the size of the target increases
Applying Fitts’s law to UI design • Bring items closer to the cursor
• Increase the target size
• Exploit the edges
Does Fitts’s law apply to mobile devices?
• Yes! Original experiment by Fitts was on human arm movement,
not mouse pointing!
• Extension to target acquisition with mouse was a big result of Card
et al. and not obvious.
• Tablet setting is closer to original experimental setting.
• No more benefit on device edges
• How device is held is important
Individual project: Planning Data Collection
Design a semi-structure interview script/survey questions that you will use
to collect data from potential users. How many questions to ask? At least
2 topic areas/ultimate goals and 3 questions per topic for an interview,
and at least 15 questions for a survey. But, you need to make sure that
you have enough questions to know about the users, their context, and
the task. If I find important topics (based on your proposal) are missing,
you will lose points.
#Disclaimer. Further instruction of this submission can be given verbally during class or through Piazza.
Individual project: Planning Data CollectionFormat
• Turn-in: a PDF of interview scripts & survey questions
• Add a title and brief description of the project idea on top
• List topics/goals and put relevant questions under the topic (Both interview &
survey) • E.g.,
Topic 1. Identify why people buy things online. Q1. What was the item that you have purchased online most recently?
Q2. xxx
Q3. xxx
Topic 2. xxx Q1. xxx
• a PDF file, 12 point scale in Times New Roman, 1.5 line spacing
#Disclaimer. Further instruction of this submission can be given verbally during class or through Piazza.
Individual project: Planning Data Collection
Rubric • Interview (5pt)
o Structure: intro-main body-closing (2pt) o Quality of questions
• Whether you ask relevant questions to your topic/problem (1pt) • Whether you ask in-depth contextual questions (1pt) • Whether the answers to questions lead to in-depth, follow-up questions (1pt)
• Survey (5pt) o Whether you used proper types of questions (e.g., open ended vs. radio button)
(2pt) o Whether you ask relevant questions to your topic/problem (2pt) o Whether you ask appropriate demographic information questions (1pt)
• You will lose 50% if your submission does not follow the format • You will lose 20% if it’s a late submission (Not accepting a late
submission submission after that) • You will lose 10% per missing an important topic Due by Midnight 10/9
#Disclaimer. Further instruction of this submission can be given verbally during class or through Piazza.