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Determining What Individual SUS Scores Mean: Adding an Adjective Rating Scale

Aaron Bangor, Philip Kortum, and James Miller

Journal of Usability Studies, Volume 4, Issue 3, May 2009, pp. 114-123

Article Contents


Results

For analysis, numerical equivalents of 1 through 7 were assigned to the adjectives from Worst Imaginable to Best Imaginable, respectively. First, a correlational analysis was conducted to determine how well the ratings (using the adjective rating scale) matched the corresponding SUS scores given by participants (i.e., via their ten individual ratings). Results are highly significant (a<0.01) with r=0.822. These results are consistent with the results found in our pilot study (Bangor, Kortum, & Miller, 2008). In the pilot study, 212 surveys were used and a correlation of r=0.806 was found between the SUS score and an identical adjective rating scale. This correlation was viewed with some caution at the time however, because only a few of the interface modes were included in the data set and there was a marked lack of data points at the extreme ends of the adjective rating scale.

The mean score for each adjective rating for the current study is listed in Table 3 and show in Figure 3.

Table 3. Descriptive Statistics of SUS Scores for Adjective Ratings*

Table 3. Descriptive Statistics of SUS Scores for Adjective Ratings*Total count equaled 959 due to 5 surveys that did not properly use the rating scale.

All of the adjectives are significantly different, except for Worst Imaginable and Awful. The seven adjectives span almost the entire 100 point range of SUS scores, although the end points have relatively few data points.

Figure 3. Mean SUS score ratings corresponding to the seven adjective ratings (error bars +/- one standard error of the mean)

Figure 3. Mean SUS score ratings corresponding to the seven adjective ratings (error bars +/- one standard error of the mean)

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