# Cumulative Impact of Testing Factors in Usability Tests for Human-Centered Web Design +
## 5 Methods and Assessor Groups
### Measurement and Scales  
As we have already described above, the differences in product features were represented by two university website layouts with the corresponding high and low aesthetic quality, as measured by the website aesthetic quality index (U-index) [12]. The university websites were pre-assessed and assigned the U-index values. To measure user performance, we employed two groups of metrics that focused on cognitive and emotional aspects of the user states, respectively. For cognitive performance, _intellectual liability_ was chosen as an indicator. Cognitive performance is an aspect of cognitive load testing that focuses on positive achievement of the assessor, evaluating, e.g., the number of correctly fulfilled tasks, as well as the number of mistakes and performance time. Intellectual liability, in its turn, describes the ability to work efficiently in the multitasking mode, switching from one task to another, as well as the ability to concentrate for a long time. The better the liability, the faster the speed and quality of the task completion [64]. Intellectual liability has been mostly researched upon in the 'practical thinking' studies within education research [65; 66; 67], especially in the Russian-speaking studies, while Western studies focused more on emotional liability. However, collaborations between those have brought to life testing methods that may be successfully applied to today's DUXU studies. Using one of these methods, we have measured intellectual ability using the test for switching attention known as the 'Schulte-Gorbov table' [68], elaborated by the renowned German psychologist [PERSON] and further developed by founders of the Soviet medical psychology, like [PERSON] and [PERSON]. We applied it before and after the experiment. The method implies that the participants pronounce figures from 1 to 25 (shown on grey squares of the table where grey and red squares are mixed) and from 24 to 1 (shown on red squares of the table), switching from grey to red and back. The time of task solution and the number of mistakes are both fixed and then are rendered into two respective scales proposed by [PERSON]/[PERSON]. The overall liability is measured for each participant individually and calculated as \(\text{A}=\text{T}-\text{C}\), where T is the scaled metric for the longevity of the test, and C is the scaled metric for the number of errors. The smaller A, the worse the performance. We have calculated A for each participant before and after the main task completion, thus detecting the drops and rises (if any) of intellectual ability. Then, we calculated \(\text{A}_{\text{mean}}\) for all the assessors in each sub-group (see below). _Emotional stress_ is the second measure of performance quality that we have applied. It refers to the level of overall stress that an assessor experiences during the task completion. However, the nature of stress is complicated, and this is why it is measured via four sub-parameters, which are called the indicators of self-esteem: In accordance with the method of self-assessment of emotional states proposed in [69], we measured, by the 1-10 Likert scales, the level of:  
* anxiety (the 'calmness/anxiety' scale);
* fatigue (the 'energy/fatigue' scale);
* arousal (the 'excitement/depression' scale);
* confidence (the'self-confidence/helplessness' scale). The scales, however, are not formed via assessors' putting marks from 1 to 10; instead, the scales consist of statements that describe emotional states and are assigned 1 to 10. This is why the scales might be imperfect and provide for answers more similar than expected (see 7.2); however, this method is more elaborated than simpler Likert scales and reflects the nature of our tasks. The four scales are, somewhat counter-intuitively, structured in a way that higher values lead to diminishment of emotional stress: That is, from 1 to 10, calmness, energy, excitement, and self-confidence grow, while anxiety, fatigue, depression, and helplessness fade.