Evaluation 1

Introduction & Usability Inspection

Objectives

By the end of class you will be able to…• Describe different usability inspection

techniques and discuss the advantages and disadvantages of usability inspection methods.

• Conduct a heuristic evaluation and cognitive walkthrough of a user interface.

What might you hope to learn from a usability evaluation?

• Is the interface…– Effective?– Engaging?– Efficient?– Easy to learn?– Equally usable by different groups?

• What problems do users have?• Suggestions to improve the interface• …

How could you evaluate an interface?

• With users– User testing (after the midterm)

• Without users– Usability inspection (today!)

• Cognitive walkthrough• Heuristic evaluation

– User modeling (Later)

Usability inspection

• A ‘discount’ method of usability evaluation where an interface is evaluated by usability experts rather than end users.

• Usually several evaluators work independently, then debrief together later.

Heuristic evaluation

• A type of usability inspection

• HCI experts (sometimes also domain experts) review an interface design with respect to a set of predefined heuristics

How many inspectors?

Jakob Nielsen - www.useit.com

Evaluation of a banking system:

How many inspectors?

Jakob Nielsen - www.useit.com

35%

75%

Heuristic Evaluation Activity

• Evaluation of Fugu

What is a cognitive walkthough (CW)?

• A type of usability inspection where experts ‘walk’ through an interface following a specified set of tasks.

• Step through the task. At each step, ask yourself four questions.

CW Questions

1. Will users be trying to produce whatever effect the action has?

2. Will users see the control (button, menu, switch, etc.) for the action?

3. Once users find the control, will they recognize that it produces the effect they want?

4. After the action, will users understand the feedback they get so they can go on to the next action with confidence?

CW Example - Rapid Transit Ticket Machine

• User wishes to purchase a round-trip ticket to Dragon Plaza.

• The ticket costs $17.50 but the user doesn’t know this yet.

• The user has only $10, but doesn’t know this yet either.

This example taken from http://asi-www.informatik.uni-hamburg.de/informatik/SE_Evaluation/html/pages/walk.htm

• User can do steps 1 and 2 in any order• Or user can enter desired fare using keypad

Step 1: Enter Destination or Journey Type

• Design Flaw no. 1: Option to indicate journey type first is not made sufficiently evident.

• Solution:

Step 2: Enter Journey Type

Step 3: Deposit money

• Design Flaw no. 2: No display of total money received.

• Solution:

Step 4: Retrieve $10 from machine since it wasn’t enough

• Design Flaw no. 3: No means of retrieving money deposited.

• Solution:

Cognitive Walkthrough Activity

Press Start

What are the advantages & disadvantages of usability

inspection?

Key points

Usability inspection…

• Is quick and inexpensive

• May miss important problems or identify false ones

• Complements user testing