A Mobile Application That Allows Children in the Early Childhood to Program Robots

Table 2

Usability attributes and associated metrics.

Usability attribute	Metrics	Usability goal
Learnability	(i) Average time used to complete a challenge the first time.; (ii) Average time of training.	(i) The average time to complete one challenge for children should be between 10 and 30 minutes.; (ii) The average time of training should be between 30 and 60 minutes.
Efficiency	(i) Total and percentage of successful challenges.; (ii) Average time to complete a challenge.	(i) Successful challenges completions should be above 70%.; (ii) The average time to complete one challenge for children should be between 10 and 20 minutes.
Memorability	Total and percentage of correct answers about the application.	The novice users should memorize at least half of the functionalities of the system, whereas the experienced users should memorize over 80%.
Errors	(i) Total and average unsuccessful attempt.; (ii) Total and average of recovery unsuccessful attempt.	(i) The average of errors be between 5 and 10 errors.; (ii) The average recovery errors by user should be above 60% of total errors.
Satisfaction	(i) Like or not like.; (ii) Difficulty level.	Percentage of satisfaction usually should be above 65%.