Component-specific usability testing. Dr Willem-Paul Brinkman Lecturer Department of Information Systems and Computing Brunel University (willem.brinkman@brunel.ac.uk). Topics. Introduction Whether and how the usability of components can be tested empirically.
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Component-specific usability testing Dr Willem-Paul Brinkman Lecturer Department of Information Systems and Computing Brunel University (willem.brinkman@brunel.ac.uk)
Topics • Introduction • Whether and how the usability of components can be tested empirically. • Testing different versions of component • Testing different components • Whether and how the usability of components can be affected by other components. • Consistency • Memory load
Usability Testing Aim to evaluate the usability of a component based on the message exchange between a user and a specific component
Two paradigms • Multiple versions testing paradigm • Single version testing paradigm Manage Create Support Re-use
Test Procedure • Normal procedures of a usability test • User task which requires interaction with components under investigation • Users must complete the task successfully
Component Component-specific component measures Number of messages received The effort users put into the interaction Objective performance Perceived ease-of-use Perceived satisfaction Control process Control loop
Component-specific component measures Component-specific questionnaire increase the statistical power because they help help the users to remember their control experience with a particular interaction component Objective performance Perceived ease-of-use Perceived satisfaction
Component-specific component measures Perceived Usefulness and Ease-of-use questionnaire (David, 1989), 6 questions, e.g. • Learning to operate [name] would be easy for me. • I would find it easy to get [name] to do what I want it to do. Unlikely Likely Objective performance Perceived ease-of-use Perceived satisfaction
Component-specific component measures Post-Study System Usability Questionnaire (Lewis, 1995) • The interface of [name] was pleasant. • I like using the interface of [name]. Strongly Strongly disagree agree Objective performance Perceived ease-of-use Perceived satisfaction
Experimental validation 80 users 8 mobile telephones 3 components were manipulated according to Cognitive Complexity Theory (Kieras & Polson, 1985) • Function Selector • Keypad • Short Text Messages
Results Average probability that a measure finds a significant (α = 0.05) effect for the usability difference between the two versions of FS, STM, or the Keypad components
Results Wilcoxon Matched-Pairs Signed-Ranks Tests between the number of correct classification made by discriminant analyses on overall and component-specific measures
Topics • Introduction • Whether and how the usability of components can be tested empirically. • Testing different versions of component • Testing different components • Whether and how the usability of components can be affected by other components. • Consistency • Memory load
Two paradigms • Multiple versions testing paradigm • Single version testing paradigm Manage Create Support Re-use
Testing Different Components • Component specific objective performance measure: • Messages received + Weight factor A common currency • Compare with ideal user A common point of reference • Usability of individual components in a single device can be compared with each other and prioritized on potential improvements
Right Mouse Button Menu Properties Assigning weight factors to represent the user’s effort in the case of ideal user {7} Set <Fill colour red, no border> {2} Call <> {1} Click <left on Fill tab> {1} Click <left on on colour red> {1} Click <left on Outline tab> {1} Click <left No Line button> {1} Click <right> {1} Click <left no Ok button> {1} Click <left on Properties option>
Properties Right Mouse Button Menu Total effort value • Total effort = MRi.W • MRi.W : Message received. Weight factor {2} Call <> {1} Click <left on Fill tab> {1} Click <left on on colour red> {1} Click <left on Outline tab> {1} Click <left No Line button> {1} Click <right> {1} Click <left no Ok button> {1} Click <left on Properties option> 5 + 2 = 7 2
Visual Drawing Objects Properties Right Mouse Button Menu Assigning weight factors in case of real user Correction for inefficiency of higher and lower components
Visual Drawing Objects Properties Right Mouse Button Menu Assigning weight factors in case of real user Inefficiency of lower level components: need more messages to pass on a message upwards than ideally required Assign weight factors as if lower components operate optimal
Visual Drawing Objects Properties Right Mouse Button Menu MRi.W #MSU ideal UE = #MSU real Assigning weight factors in case of real user Inefficiency of higher level components: more messages are requested than ideally required • UE : User effort • MRi.W : Message received. Weight factor • #MSUreal :Number of messages sent upward by real user • #MSUideal :Number of messages sent upward by ideal user
The total effort an ideal user would make The total effort a real user made The extra effort a real user made Prioritize Ideal User versus Real User • Extra User Effort = User Effort - Total effort Calculate for each component:
Experimental validation 40 users 40 mobile telephones 2 components were manipulated (Keypad only Repeated-Key Method) • Function Selector • Short Text Messages
Results Partial correlation between extra user effort regarding the two components and other usability measures *p. < .05. **p. < .01.
Comparison with other evaluation methods Overall measures Sequential Data analysis GOMS Thinking-aloud, Cognitive Walkthrough and heuristic evaluation Example: Keystrokes, task duration, overall perceived usability Relatively easy to obtain Unsuitable to evaluate components
Comparison with other evaluation methods Overall measures Sequential Data analysis GOMS Thinking-aloud, Cognitive Walkthrough and heuristic evaluation Based only on lower-level events Pre-processing: selection, abstraction, and re-coding Relation between higher-level component and compound message less direct Components’ status not recorded
Comparison with other evaluation methods Overall measures Sequential Data analysis GOMS Thinking-aloud, Cognitive Walkthrough and heuristic evaluation Help to understand the problem Only looking at error-free task execution Considers the system only at the lowest-level layer
Comparison with other evaluation methods Overall measures Sequential Data analysis GOMS Thinking-aloud, Cognitive Walkthrough and heuristic evaluation Quicker Evaluator effect (reliability)
Topics • Introduction • Whether and how the usability of components can be tested empirically. • Testing different versions of component • Testing different components • Whether and how the usability of components can be affected by other components. • Consistency • Memory load
