Usability Notes
Lecture 1 : Introduction
What is usability? → Ease of use
Usability =
The extent to which a product can be used by specified users to achieve specific goals
with effectiveness, efficiency, and satisfaction in a specified context of use.
Usability goals (6)
1. Effective? → does it do what it should do?
2. Efficient? → optimale usage?
3. Safe to use? → protection from making errors?
4. Right functionality? → can a user do much with
it?
5. Is it easy to learn to use?
6. Is its usage easy to remember?
Usability: part of Interaction Design =
Designing interactive products to support the
way people communicate and interact in their
everyday and working lives (Sharp, Rogers and
Preece).
Usability: part of user experience =
Hoe ervaren mensen een product?
○ Besides, usability also focuses on enjoyment and satisfaction during use (e.g.
looks, holding it, open/close etc.)
○ Every product that is sued by someone has a user experience
User experience doelen =
○ Wanted aspects → pleasant, fascinating, fun, helpful, motivating, etc.
○ Unwanted aspects → boring, frustrating, unpleasant, etc.
Differences between usability & user experience =
○ Potential conflicts → can a product be enjoyable as well as safe?
○ Different goals and how to measure these
,Usability concepts
Affordance =
The quality or property of an object that defines its possible uses or makes clear how it
can or should be used
○ Possibilities that are easy to discover
○ Indication of use without explanation
Visual affordances =
Observed and present properties of an object that indicate how you use it
→ e.g. chair > sit on it / lift it, button > turn / press
Physical affordances = een kopje, een stoel, een deurknop
Virtual affordances = een pauzeknop, een plaatje van een prullenbak op de computer,
een scrollbalk.
Norman =
If a simple object like a door needs instructions, then it probably indicates a poor design.
Design for humans → 2 basic principles by Norman =
1. Make the method of use visible (e.g. by affordances)
2. Use a good conceptual model
Conceptual model =
People make their own image of how something works. Understanding its precise
operation is not necessary.
→ e.g. turning the steering wheel turns the wheels; engineers have a more detailed
concept than most people, but the way you “use” a car is the same.
Example with scissors =
○ Affordances → holes allow fingers to be inserted
○ Constraints → large hole for multiple fingers, small hole for the thumb
○ Conceptual model → suggest usage by parts and how they are connected
Visibility =
Hidden functions lead to problems
→ e.g. when number of functions is greater than number of buttons
○ With visible functionality, the user does not have to remember the use of an
object
→ e.g. bathroom faucets (2 functions): hot/cold & on/off
Mapping =
Relationship between button and action/result
, Feedback =
Let a user know what is happening
→ e.g. beep (phone/atm machine/tran self check-in, etc.), light (elevator/caps lock),
display (printer)
Can also be physical change
→ e.g. turned knob, switch, stove flames are visible
Constraints =
Limitation of the number of possible actions → beperking van het aantal mogelijke acties
→ prevent selection of wrong options (e.g. sleutel, VGA vs. USB, inactieve software
opties)
Consistency =
Design interfaces with similar functions and elements for similar tasks
Internal consistency = operations behave the same within an application
External consistency = operations/interfaces/etc. are similar in several
applications/machines
Conventions =
Accepted norms of standards (can be artificial, arbitrary, learned)
→ often determined by culture (e.g. drive on the right side of the road, scrollbar on the
right side of the screen, the color red indicating danger)
○ Norman: use conventions with respect, violate them only with great risk
Execution-Evaluation cycles (Norman) =
Gulf of execution =
How to translate the goals to the actions
Gulf of evaluation =
Did the right thing happen?
Goals = what we want to happen
Execution = what we do to the world
Evaluation = Comparing what happened with
what we wanted to happen
The seven stages of action
1. Goal (form the goal)
2. Plan (the action)
3. Specify (an action sequence)
4. Perform (the action sequence)
5. Perceive (the state of the world)
6. Interpret (the perception)
7. Compare (the outcome with the goal)
, Conclusion
○ Display current status and alternatives
○ A good conceptual model is necessary
○ Use mapping to indicate relationships
○ User must receive continuous feedback
○ Use affordances
Designing remains challenging
○ Ever increase of number of functions (e.g. phones, watches)
○ Display usually virtual
○ Often limited display space available
○ Still many errors
Individual differences
○ Designers cannot satisfy every user
○ Designers do often not represent the group they are designing for
○ Don’t expect every user to use or think like you do
○ People differ both mentally and physically
Norman: need 5 or 6 tries for a design to work properly → that may not always be possible in
practice (competition/costs etc.)
Lecture 2 : Interfaces
Interface =
Place where communication takes place between independent systems (such as people
and machines)
User interface or Human-Computer Interface (HCI) =
Part in which people communicate/interact with systems/machines
○ Hardware als software
○ Input (e.g. gebruiker stuurt systeem aan)
○ Output (e.g. systeem toont effect van aansturing)
User interface + usability =
Extent to which the design of a user interface takes into account the psychological and
physical characteristics of people, as well as attention for..:
○ Effectiveness
○ Efficiency
○ Pleasant use
Three levels of processing
1. Visceral level =
Instant, automatic reactions.
○ It’s your gut feeling (e.g. fear when you hear a loud noise)
○ Fast and subconscious
Lecture 1 : Introduction
What is usability? → Ease of use
Usability =
The extent to which a product can be used by specified users to achieve specific goals
with effectiveness, efficiency, and satisfaction in a specified context of use.
Usability goals (6)
1. Effective? → does it do what it should do?
2. Efficient? → optimale usage?
3. Safe to use? → protection from making errors?
4. Right functionality? → can a user do much with
it?
5. Is it easy to learn to use?
6. Is its usage easy to remember?
Usability: part of Interaction Design =
Designing interactive products to support the
way people communicate and interact in their
everyday and working lives (Sharp, Rogers and
Preece).
Usability: part of user experience =
Hoe ervaren mensen een product?
○ Besides, usability also focuses on enjoyment and satisfaction during use (e.g.
looks, holding it, open/close etc.)
○ Every product that is sued by someone has a user experience
User experience doelen =
○ Wanted aspects → pleasant, fascinating, fun, helpful, motivating, etc.
○ Unwanted aspects → boring, frustrating, unpleasant, etc.
Differences between usability & user experience =
○ Potential conflicts → can a product be enjoyable as well as safe?
○ Different goals and how to measure these
,Usability concepts
Affordance =
The quality or property of an object that defines its possible uses or makes clear how it
can or should be used
○ Possibilities that are easy to discover
○ Indication of use without explanation
Visual affordances =
Observed and present properties of an object that indicate how you use it
→ e.g. chair > sit on it / lift it, button > turn / press
Physical affordances = een kopje, een stoel, een deurknop
Virtual affordances = een pauzeknop, een plaatje van een prullenbak op de computer,
een scrollbalk.
Norman =
If a simple object like a door needs instructions, then it probably indicates a poor design.
Design for humans → 2 basic principles by Norman =
1. Make the method of use visible (e.g. by affordances)
2. Use a good conceptual model
Conceptual model =
People make their own image of how something works. Understanding its precise
operation is not necessary.
→ e.g. turning the steering wheel turns the wheels; engineers have a more detailed
concept than most people, but the way you “use” a car is the same.
Example with scissors =
○ Affordances → holes allow fingers to be inserted
○ Constraints → large hole for multiple fingers, small hole for the thumb
○ Conceptual model → suggest usage by parts and how they are connected
Visibility =
Hidden functions lead to problems
→ e.g. when number of functions is greater than number of buttons
○ With visible functionality, the user does not have to remember the use of an
object
→ e.g. bathroom faucets (2 functions): hot/cold & on/off
Mapping =
Relationship between button and action/result
, Feedback =
Let a user know what is happening
→ e.g. beep (phone/atm machine/tran self check-in, etc.), light (elevator/caps lock),
display (printer)
Can also be physical change
→ e.g. turned knob, switch, stove flames are visible
Constraints =
Limitation of the number of possible actions → beperking van het aantal mogelijke acties
→ prevent selection of wrong options (e.g. sleutel, VGA vs. USB, inactieve software
opties)
Consistency =
Design interfaces with similar functions and elements for similar tasks
Internal consistency = operations behave the same within an application
External consistency = operations/interfaces/etc. are similar in several
applications/machines
Conventions =
Accepted norms of standards (can be artificial, arbitrary, learned)
→ often determined by culture (e.g. drive on the right side of the road, scrollbar on the
right side of the screen, the color red indicating danger)
○ Norman: use conventions with respect, violate them only with great risk
Execution-Evaluation cycles (Norman) =
Gulf of execution =
How to translate the goals to the actions
Gulf of evaluation =
Did the right thing happen?
Goals = what we want to happen
Execution = what we do to the world
Evaluation = Comparing what happened with
what we wanted to happen
The seven stages of action
1. Goal (form the goal)
2. Plan (the action)
3. Specify (an action sequence)
4. Perform (the action sequence)
5. Perceive (the state of the world)
6. Interpret (the perception)
7. Compare (the outcome with the goal)
, Conclusion
○ Display current status and alternatives
○ A good conceptual model is necessary
○ Use mapping to indicate relationships
○ User must receive continuous feedback
○ Use affordances
Designing remains challenging
○ Ever increase of number of functions (e.g. phones, watches)
○ Display usually virtual
○ Often limited display space available
○ Still many errors
Individual differences
○ Designers cannot satisfy every user
○ Designers do often not represent the group they are designing for
○ Don’t expect every user to use or think like you do
○ People differ both mentally and physically
Norman: need 5 or 6 tries for a design to work properly → that may not always be possible in
practice (competition/costs etc.)
Lecture 2 : Interfaces
Interface =
Place where communication takes place between independent systems (such as people
and machines)
User interface or Human-Computer Interface (HCI) =
Part in which people communicate/interact with systems/machines
○ Hardware als software
○ Input (e.g. gebruiker stuurt systeem aan)
○ Output (e.g. systeem toont effect van aansturing)
User interface + usability =
Extent to which the design of a user interface takes into account the psychological and
physical characteristics of people, as well as attention for..:
○ Effectiveness
○ Efficiency
○ Pleasant use
Three levels of processing
1. Visceral level =
Instant, automatic reactions.
○ It’s your gut feeling (e.g. fear when you hear a loud noise)
○ Fast and subconscious
