To understand usability it is important to not only measure user
performance (effectiveness and efficiency) but also satisfaction.
Established questionnaires will give more reliable and repeatable
results than ad hoc questionnaires.
Overall satisfaction: SUS
(System Usability Scale) is a 10-item questionnaire that gives
an overview of satisfaction with software. It was developed
Brooke, and is freely available for use providing acknowledgement
is made of the source. Nigel
Bevan is collecting data for norms
Satisfaction profile: SUMI
(Software Usability Measurement Inventory) is a 50 item questionnaire
that measures five aspects of user satisfaction (Likability, Efficiency,
Helpfulness, Control and Learnability), and scores them against
expected industry norms. It can be purchased from HFRG. The INUSE
Handbook explains how
to use SUMI.
User interface satisfaction: QUIS
(Questionnaire for User Interaction Satisfaction) is similar to
SUMI, but measures attitude towards eleven interface factors (screen
factors, terminology and system feedback, learning factors, system
capabilities, technical manuals, on-line tutorials, multimedia,
voice recognition, virtual environments, internet access, and software
installation). It does not have industry norms. QUIS can be purchased
from the University of Maryland.