INTERACTION D ESIGN
1 Evaluation: Usability Testing and Field Studies U SABILITYT ESTING
Involves recording performance of typical
users doing typical tasks.
Controlled environmental settings.
Users are observed and timed.
Data is recorded on video & key presses
The data is used to calculate performance
times, and to identify & explain errors.
User satisfaction is evaluated using
questionnaires & interviews.
Field observations may be used to provide 2
contextual understanding. U SABILITYTESTING C HARACTERISTICS
Goals & questions focus on how well users
perform tasks with the product.
Comparison of products or prototypes
Focus is on time to complete task & number
& type of errors.
Data collected by video & interaction
User satisfaction questionnaires &
interviews provide data about users’
opinions. 3 EXPERIMENTS AND USABILITY TESTING
Experiments test hypotheses to discover
new knowledge by investigating the
relationship between two or more things –
Usability testing is applied
Developers check that the system is
usable by the intended user population for
Experiments may also be done in usability
4 U SABILITY TESTING VS . RESEARCH
Usability testing Experiments for
Improve products Discover knowledge
Few participants Many participants
Results inform design Results validated
Usually not completely statistically
replicable Must be replicable
Conditions controlled as Strongly controlled
much as possible conditions
Procedure planned Experimental design
Results reported to Scientific reported 5o
developers scientific community USABILITY LAB WITH OBSERVERS
WATCHING A USER& ASSISTANT
6 PORTABLE EQUIPMENT FOR USE IN THE
7 8 TESTING CONDITIONS
Usability lab or other controlled space.
selecting representative users;
developing representative tasks.
5-10 users typically selected.
Tasks usually last no more than 30
The test conditions should be the same for
Informed consent form explains 9
procedures and deals with ethical issues. SOME TYPE OF DATA
Time to complete a task.
Time to complete a task after a specified
time away from the product.
Number and type of errors per task.
Number of errors per unit of time.
Number of navigations to online help or
Number of users making a particular
Number of users co