SUMI

Method suitability

Study type

XField studies
XLab studies
XOnline studies
XQuestionnaire

Development phase

Concepts
Early prototypes
XFunctional prototypes
XProducts on market

Studied period of experience

Before usage
XSnapshots
XAn episode
Long-term UX

Evaluator / Info provider

UX experts
XOne user at a time
Groups of users
Pairs of users

Data

Qualitative
XQuantitative

Applications

XWeb services
XPC software
Mobile software
Hardware designs
Other:

Requirements

Trained researcher
Special equipment

Summary

Satisfaction is a part of classic definition of usability since a long time. SUMI (Software Usability Measurement Inventory) has been developed to provide an authoritative, standardised measurement of user satisfaction with software. It can be used for the evaluation and comparison of products (or versions of a product) and to set and track verifiable targets regarding satisfaction. SUMI is a classical Likert-type measure of attitude toward a software package. The questionnaire comprises five subscales: efficiency, affect, helpfulness, control and learnability. SUMI analysis also provides a “global” satisfaction score.

Description

The SUMI is a 50 items Likert-type questionnaire. Users of a product should indicate their agreement with 50 statements such as “I enjoy my sessions with this software.” or “It takes too long to learn the software commands.” using a three- point format (“agree”, “don't know” and “disagree”). Each subscale is represented by 10 items. The “affect” subscale is supposed to measure “the user's general emotional reaction to the software” or the “likeability” of the software. Additionally, 25 items are used to calculate a general usability or satisfaction score. The developers of the SUMI recommend administering the questionnaire to a group of 12 participants directly after a test with the product and before any debriefing interview. It can also be used in a survey, with larger groups of respondents.

Strengths

validated instrument; database with results available for comparison of own test results

Weaknesses

same drawbacks as with all subjective scales; focus mainly on software; scale mostly addresses classical usability issues, smaller part is about affect; the results are not highly informative for redesigners

References describing the method

Kirakowski, J. & Corbett, M. (1993). SUMI - The Software Usability Measurement Inventory. British Journal of Educational Technology, 24 (3), 210-212.
Kirakowski, J. (1994). The Use of Questionnaire Methods for Usability Assessment. Book chapter available on http://sumi.ucc.ie/.
http://sumi.ucc.ie/

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