![]() It is in these situations, where a facilitator elicits verbal responses or the participant responds with pen and paper, that otherwise hidden logistics issues may become apparent. During the system development phase, it may be administered manually, e.g., during usability testing or other validation activities. The SUS can be administered electronically, which is common in post-deployment situations where the researcher wants to conduct a usability evaluation with a large base of system users. The SUS is a 10 item, 5-point Likert scale anchored with 1= Strongly Disagree and 5 = Strongly Agree and is used to evaluate a system’s usability in a relatively quick and reliable fashion (Brooke, 1996). The Information Technology department at Intel® Corporation has employed the System Usability Scale (SUS) for the subjective component of some of its internal usability evaluations. Practitioners can quickly test Likert items through verbal protocols by using interpolations as a metric.Seven-point Likert scales appear to be more suited to electronic distribution of usability inventories.Seven-point Likert scales appear to be sensitive enough to record a more accurate evaluation of an interface while remaining relatively compact.Interpolations provide evidence that 5-point Likert scales may not be sensitive enough to record a usability test participant’s true evaluation of a system.Interpolations are problematic because they cannot be mitigated within an electronic survey medium and require interpretation with facilitated surveys.Five-point Likert scales are more likely than 7-point scales to elicit interpolations in usability inventories.The following are the main findings of this study: This finding supported the conclusion that 7-point Likert items provide a more accurate measure of a participant’s true evaluation and are more appropriate for electronically-distributed and otherwise unsupervised usability questionnaires. In an applied setting, this implied that electronic radio-button style survey tools using 5-point items might not be accurately measuring participant responses. Participants in the 5-point scale condition were more likely than those presented with the 7-point scale to interpolate, i.e., attempt a response between two discrete values presented to them. The original instrument with its 5-point Likert items was presented, as well as an alternate version modified with 7-point Likert items. A series of usability tests was run on two enterprise software applications, followed by verbal administration of the System Usability Scale.
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