# Evaluation of Methodologies and Measures on the Usability of Social Robots: A Systematic Review
## 3 Results
### Evaluation Dimensions
#### 3.3.3. Most Frequently Used Measures from Recent Studies  
There are 167 measures from 36 articles we reviewed after removing duplicated items. Most of the measures used are Likert scale and some are based on semantic differential techniques which included pairs of words that are opposite in meaning. Before categorizing the measured variables, we will review 3 measures which were mostly used to evaluate a social robot: (1) Enjoyment, (2) Ease of use, and (3) Trust. Enjoyment. Refs. [9; 18; 23; 27; 37; 49; 50] The concept of enjoyment of use originated from the hedonic system by [PERSON] [45] wherein it was considered as a crucial determinant for the Intention to Use. The influence of enjoyment of use on the intention to use varies depending on whether the subject is a hedonic system or a utilitarian system. According to previous research [44; 47], perceived enjoyment didn't show direct influence on Intention to use, but it had an influence on ease of use and usefulness. Ref. [49] evaluated user acceptance on a huggable robot, Hugvie with three main dimensions: intention to use, enjoyment of use and ease of use. Enjoyment of use had four subordinate measures: enjoy, interested, bored, have fun. Ref. [18] found so perceived enjoyment as a factor which has an effect on the intention to use. Ref. [9] adopted Almere model and they found that enjoyment was a measure which has an influence on user acceptance. Ref. [50] evaluated several aspects of human-robot interaction, and enjoyment was a measure to evaluate the interaction between user and robots. Ease of use. Refs. [9; 17; 23; 28; 49; 51; 52] Ease of use was one of the main dimensions in TAM, and it was defined as: the degree to which a person believes that using a particular system would be free of effort. TAM also suggests that the definition of \"ease\" is \"freedom from difficulty or great effort\" [39]. In UTAUT, ease of use was defined as the degree to which an innovation is expected to be free of effort [53]. Ease of use was one of the important determinants of user acceptance in UTAUT and Almere model. Ease of use is a concept which accepted widely, and its definition is varied. Some research considered ease of use as a substitute to the concept of usability, while others defined ease of use as a sub-measure of usability. Along with ease of use, effectiveness and efficiency were also considered as sub-measures of usability. Effectiveness is a quantitative measurement that is measured using the task completion rate. Efficiency is also a quantitative measure and is defined as the task completion time. However, ease of use is a qualitative and subjective measure. Ease of use measures task-performance satisfaction [54]. Ref. [49] adopted ease of use as one of three main dimensions and ease of use had two sub-measures: easy, easily understand how to use. Ref. [17] used SUS (System usability scale) and SUS define ease of use as one of 10 sub-measures to evaluate usability. In [17], SUS score was processed to be on a scale of 0-100. Ref. [51] defined four main variables as similarity, friendship, usability, and motivation. Ease of use is was sub-measure of usability. For usability evaluation, ref. [51] used SUS and participants were asked to respond on a 5-point Likert-scale. Ref. [23] evaluated a social robot with three dimensions: attitudinal