Evaluation in HCI Angela Kessell Oct. 13, 2005. Evaluation Heuristic Evaluation Measuring API...

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Evaluation in HCI

Angela Kessell

Oct. 13, 2005

Evaluation

• Heuristic Evaluation

• Measuring API Usability

• Methodology Matters: Doing Research in the Behavioral and Social Sciences

Evaluation

• Heuristic Evaluation– “Discount usability engineering method”

• Measuring API Usability

Evaluation

• Measuring API Usability– Usability applied to APIs

Evaluation

• Measuring API Usability– Usability applied to APIs

• Methodology Matters: Doing Research in the Behavioral and Social Sciences– Designing, carrying out, and evaluating

human subjects studies

Heuristic EvaluationJakob Nielsen

Most usability engineering methods will contribute substantially to the usability of an interface …

Heuristic EvaluationJakob Nielsen

Most usability engineering methods will contribute substantially to the usability of an interface …

…if they are actually used.

Heuristic Evaluation

• What is it?

• What is it?A discount usability engineering method

- Easy (can be taught in ½ day seminar)

- Fast (about a day for most evaluations)

- Cheap (e.g. $(4,000 + 600i))

• How does it work?

• How does it work?– Evaluators use a checklist of basic usability

heuristics – Evaluators go through an interface twice

• 1st pass get a feel for the flow and general scope• 2nd pass refer to checklist of usability heuristics and

focus on individual elements

– The findings of evaluators are combined and assessed

Heuristic EvaluationUsability Heuristics (original, unrevised list)

• Simple and natural dialogue• Speak the users’ language• Minimize the users’ memory load• Consistency• Feedback• Clearly marked exits• Shortcuts• Precise and constructive error messages• Prevent errors• Help and documentation

Heuristic EvaluationUsability Heuristics (original, unrevised list)

• Simple and natural dialogue• Speak the users’ language• Minimize the users’ memory load• Consistency• Feedback• Clearly marked exits• Shortcuts• Precise and constructive error messages• Prevent errors• Help and documentation

COMMENTS?

• One expert won’t due• Need 3 - 5 evaluators• Exact number needed

depends on cost-benefit analysis

• Who are these evaluators?– Typically not domain experts / real users– No official “usability specialist” certification

exists

• Optimal performance requires double experts

• Debriefing session– Conducted in brain-storming mode– Evaluators rate the severity of all problems

identified– Use a 0 – 4, absolute scale

• 0 I don’t agree that this is a prob at all• 1 Cosmetic prob only• 2 Minor prob – low priority• 3 Major prob – high priority• 4 Usability catastrophe – imperative to fix

• Debriefing session– Conducted in brain-storming mode– Evaluators rate the severity of all problems

identified– Use a 0 – 4, absolute scale

• 0 I don’t agree that this is a prob at all• 1 Cosmetic prob only• 2 Minor prob – low priority• 3 Major prob – high priority• 4 Usability catastrophe – imperative to fix

COMMENTS?

• How does H.E. differ from User Testing?

• How does H.E. differ from User Testing?– Evaluators have checklists – Evaluators are not the target users – Evaluators decide on their own how they want

to proceed – Observer can answer evaluators’ questions

about the domain or give hints for using the interface

– Evaluators say what they didn’t like and why; observer doesn’t interpret evaluators’ actions

• What are the shortcomings of H.E.?

• What are the shortcomings of H.E.?– Identifies usability problems without indicating

how they are to be fixed. • “Ideas for appropriate redesigns have to appear

magically in the heads of designers on the basis of their sheer creative powers.”

– Cannot expect it to address all usability issues when evaluators are not domain experts / actual users

Measuring API Usability Steven Clarke

• User-centered design approach– Understanding both your users and the way

they work

• Scenario-based design approach– Ensures API reflects the tasks that users want

to perform

• Use Cognitive Dimensions Framework

Measuring API Usability

• Cognitive dimensions framework describes:

– What users expect– What the API actually

provides

• Cognitive dimensions framework provides:

– A common vocabulary for developers

– Draws attention to important aspects

The Dimensions:– Abstraction level– Learning style– Working framework– Work-step unit– Progressive evaluation– Premature commitment– Penetrability– API elaboration– API viscosity– Consistency– Role expressiveness– Domain correspondence

• Cognitive dimensions framework describes:

– What users expect– What the API actually

provides

• Cognitive dimensions framework provides:

– A common vocabulary for developers

– Draws attention to important aspects

The Dimensions:– Abstraction level– Learning style– Working framework– Work-step unit– Progressive evaluation– Premature commitment– Penetrability– API elaboration– API viscosity– Consistency– Role expressiveness– Domain correspondence

COMMENTS?

• Use Personas:– Profiles describing the

stereotypical behavior of three main developer groups (Opportunistic, Pragmatic, Systematic)

• Compare API evaluation with the profile requirements

• Use Personas:– Profiles describing the

stereotypical behavior of three main developer groups (Opportunistic, Pragmatic, Systematic)

• Compare API evaluation with the profile requirements

COMMENTS?

Methodology Matters: Doing Research in the Behavioral and Social Sciences

Joseph McGrath

Key points:

• All methods are valuable, but all have limitations/weaknesses

• Offset the weaknesses by using multiple methods

In conducting research, try to maximize:

• Generalizability

• Precision

• Realism

In conducting research, try to maximize:

• Generalizability

• Precision

• Realism

-You cannot maximize all three simultaneously.

From http://pages.cpsc.ucalgary.ca/%7Esaul/hci_educ_papers/bgbg95/mcgrath-summary.pdf

• 1st 2 papers focus on computer programs / GUIs

• 3rd paper presents the whole gamut of methodologies available to study any human behavior

But… what’s missing?

But…

• Where are the statistics?

• Are there objective “right” answers in HCI?

• How do we evaluate other kinds of interfaces?

• Other thoughts on what’s missing?

How do we evaluate…

• “Embodied virtuality” / ubiquitous computing “interfaces”

• (Aura video… http://www.cs.cmu.edu/~aura/)

• Try to pick out one capability presented, and think about how you might evaluate it

Evaluating Aura

• Do we evaluate the whole system at once? Or bit by bit?

• Where / What is the interface?

• Is anyone not a target user?

From http://www.usability.uk.com/images/cartoons/cart5.htm

Evaluation in HCI Angela Kessell Oct. 13, 2005. Evaluation Heuristic Evaluation Measuring API...

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