5. Discussions and conclusion
In this paper, we analyzed the possibility of predicting workers' stress and workload levels, as well as changes in these conditions, by means of time-series statistics computed from unobtrusively collected physiological and behavioral data in a smart office environment. The research questions in hands are of great interest to today's society where stress is becoming increasingly present and harmful, but are also pertinent to the current state of the art in ambient intelligence and smart environments. Unobtrusive monitoring of peoples' behavior and physiology is already possible, but we yet need to associate these patterns to the disorder of interest. Moreover, it is still necessary to clarify and limit the use of the proposed system to avoid ethical and privacy issues before is implementation (Alberdi et al., 2015). Results show that the prediction of perceived stress and workload levels is possible using change and variability patterns of data collected unobtrusively from smart offices.
A regression analysis of the target scores from smart office data showed many statistically significant results, enforcing the hypothesis that this kind of collected data can actually predict the perceived stress and workload levels. The correlations found by this analysis vary from moderate to strong, depending on the nature of the objective label. NasaTLX scores, together with effort, mental effort and valence were the best-predicted scores, whereas self-reported stress and performance didn't show enough statistical significance to be considered predictable. In case of stress prediction, this is not surprising, as this label was acquired by means of a single-question visual analog scale, which unlike NasaTLX, RSME or VAS questionnaires, is not a questionnaire whose reliability has been verified and might be too subjective to be well capturing the real perceived stress levels of the users. Nonetheless, the analyses on the standardized scores improved the previous results, even demonstrating predictability for the self-reported stress and performance levels. This reasserts the fact that there is some inter-subject variability present on every score used for the study, but also suggests that controlling for this variability by means of standardization methods, can make their prediction possible.