# Activity Recommendation Model Using Rank Correlation for Chronic Stress Management
## 3 Activity Recommendation Model using Rank Correlation for Chronic Stress Management
### Activity Recommendation Model for Chronic Stress Management  
The activity recommendation model for stress management employs Spearman's rank correlation coefficient to recommend a proper activity to a user through the inferred correlation. Figure 5 shows an activity recommendation model using rank correlation for chronic stress management.  
The objective of this model is to keep a user's PSS 13 points or less. Through the change in the value of PSS, the inducement direction of AISM is determined. If a PSS value is 13 or less [6], the model recommends the activities similar to AISM and induces a further reduction in the value of PSS. If a PSS value ranges from 14 to 16 (mild stress) [8], lasting the stress long causes much exposure to Distress, and thereby the PSS value is likely to increase. Accordingly, the model recommends a user's activities that reduced a PSS value based on the user's history of records and other users' good AISM. A bPSS value ranging from 17 to 18 means moderate stress which requires cautious attention [30]. This value can easily go up if a PSS value is high. For this reason, in the intermediate step before the PSS calculation, it can exceed 19 points. Therefore, the moderate stress (PSS ranging  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**No.** & **PASM** & **PSS** & **S (PASM, PSS)** & **NASM** & **PSS** & **S (NASM, PSS)** \\ \hline
1 & Increased & Increased & +0.34 & Increased & Decreased & \(-0.42\) \\
2 & Increased & Decreased & +0.89 & Decreased & Decreased & \(-0.91\) \\
3 & Increased & Increased & +0.26 & Increased & Not changed & \(-0.03\) \\
4 & Decreased & Increased & +0.59 & Decreased & Increased & \(-0.39\) \\
5 & Increased & Not changed & +0.15 & Increased & Not changed & \(-0.04\) \\
6 & Decreased & Decreased & +0.41 & Decreased & Decreased & \(-0.87\) \\
7 & Not changed & Not changed & +0.06 & Increased & Not changed & \(-0.08\) \\
8 & Decreased & Increased & +0.77 & Not changed & Increased & \(+0.02\) \\
9 & Increased & Not changed & +0.09 & Increased & Not changed & \(+0.01\) \\
10 & Not changed & Increased & \(-0.02\) & Decreased & Not changed & \(-0.12\) \\
11 & Increased & Decreased & +0.73 & Increased & Decreased & \(-0.21\) \\... &... &... &... &... &... \\ \hline \end{tabular}
\end{table}
Table 2: Correlation coefficient of S (PASM, PSS), S (NASM, PSS).  
Figure 5: Activity recommendation model using rank correlation for chronic stress management.  
in the same way as the extremely severe stress (19), and the model finds and recommends the AISM which helped to reduce the most a PSS with the use of collaborative filtering and recommends a user to have professional help. A user who scores 17 or more of PSS at least is classified in a risk group so that the user's stress is managed in consideration of any little change in a PSS value. As such, the model recommends personalized activities by using a user's current PSS, the difference between bPSS and aPSS, and records of AISM. If there is a lack of data about a user, the model employs collaborative filtering to compare other users' records and the user's current status and to recommend the most appropriate AISM, and therefore the proposed model solves cold start problem and accomplishes precise recommendation [31; 32].