As you might have noted
from one of my previous blogs (SUS), I am a big fan of usability analyses and
statistics. One thing I have found time and time again, is that it can be very
difficult to get participants to take surveys seriously. There often seems to
be a sweet spot when the user has less than 5 questions, but over 10 questions
and, whether you want to admit it or not, the number of bad data participants
increases exponentially. That said, I came across a study recently by
researchers at Intel that encountered a similar problem when attempting to
incorporate a 10-item, five-point Likert scale called the System Usability
Scale (SUS). To solve this, they decided to empirically reduce the number of
questions by using only the highest correlating questions from a modified
version of the SUS. The SUS was chosen because it had been extensively tested,
and has proven to be a reliable representation of user satisfaction and system
usability. However, by cutting down the number of questions from the SUS, it
would also reduce the amount of data points, to help offset this, the Likert
scales increased from 5 to 7 points. Increasing to a 7 point Likert was also
heavily backed up by previous research (see Diefenbach et al. (1993), Cox
(1980)). The results of the research was titled the Usability Metric for User
Experience (UMEX).
It was concluded that
the UMEX is a “reliable, valid, and sensitive alternative to the System
Usability Scale.” It has a high correlation with SUS at that of above 0.80.
Because of this, it is suggested that the UMEX is fully capable as acting as a
standalone application for usability testing. More so, because of its compact
size and ease of application, the Umex is attributed by a fundamental
requirement by the Use Experience community: “in order to measure user
experience effectively, its components need to be measured efficiently.”
I have not ever used the
UMEX or anything like it. I can not say it should be used, I just think someone
doing a quick and dirty study might like using it.
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