## 4 Results
### User-Engagement Calculations to Assess Educational Web Project Parts Interaction  
Both reliability and availability metrics are valuable in the application of performance management and monitoring. However, both are different from each other, because a piece of technical equipment may be available but not reliable. For example, we could consider a case where we suppose we do have equipment X, which has a frequent connection loss for 6 min every hour. That means 90% availability, but less than 1 h of reliability, which is a poor indicator value for e-commerce. Self-education e-resources have been in demand especially since the start of the Covid-19 crisis. For instance, registration on the popular educational platform Coursera, which underwent a partnership with various universities during the Covid-19 quarantine period, is up by 173% in March 2020, while course enrollment increased by 145% compared to February the same year [34]. In the study, we analyzed the 2017 business and finance courses data from an educational platform Udemy in order to obtain the user-engagement score and perform association tests for the obtained values with the subscription and review count, prices, and course duration. This allowed us to validate the user-engagement score as an unbiased metric for web project assessment and correlation with technical condition data. We investigated how the user-engagement score might affect the increase in efficiency of careful Service Level Objectives definition and computation. Also, we evaluated various indicators and strategies to assess infrastructure technical conditions based on the correlation between SLO/SLA and user-engagement scores. The developed framework is to help identify possible system issues and improve regular downtimes management. According to Google Trends statistics, the peak of popularity of the platform from 2017 to 2020 inclusive was reached in late March-early April 2020 and was 100%. Thus, the losses due to the unavailability of the service can be much greater than in the normal period. Therefore, the implementation of technical condition assessment using site reliability and SLO methods is necessary for the full services and information product provision. We found that in 2017 Udemy business and finance domain courses data, there are 1195 observations out of which 94.85% entities have a label \"paid\", although, the user enrollment in paid courses is 75.58%. The average cost of a studied online course was $120, and the median and the mode were $124 and $200, respectively. In the majority of cases, online classes that were published earlier in the year had more students signed up by the end of the year. In addition, 0.03% of free courses had a higher than average number of subscribers and even exceeded subscriptions to paid courses. This indicates that if the web project training is free and the user believes that its material is well-structured enough, it is more likely that a person will register for the class, and not for a paid one. In turn, this will create a load on the infrastructure, induce more course enrollments, but can be less profitable to an e-learning service provider.  
The paid course duration takes longer compared to free ones. We determined the total sum of hours required for each registered participant to complete the course. The number of subscribers is multiplied by the course duration to calculate this. The total number of subscribers was 668,938, so the entire time for all users' course completions was 3,754,806 h.  
On average, one hour of paid content costs a user $18.6. Assume that a 1% loss of availability can block users from enrolling or attending the selected class, a loss in profit will be about $123,700 per hour, according to our data.  
A detailed data examination revealed that the most expensive courses are at the expert level, and in terms of duration they are in the interval of 1-100 h, while classes with a longer span (\(\sim\)200-300 h) are only beginner level and cost less by about $20 than those in less long courses.