# Effect of COVID-19 on Selected Characteristics of Life Satisfaction Reflected in a Fuzzy Model
###### Abstract
Due to the specificity of psychological research, many of it is based on questionnaire assessment. In such cases, the linguistic model--the basis for the fuzzy system--is already pre-prepared. By using questionnaires as a data source, we have access to a linguistic description of the dependencies and results. This description is the result of years of experience of the scientists who develop these questionnaires. To preserve this knowledge and experience in the created digital model, in the presented research, we used a tool such as the fuzzy sets and the fuzzy systems. Their main advantage is the ability to define rules based on a linguistic description. In this way, it is possible to propose an algorithm/model while maintaining the intuitions and assumptions of data sources that are not described by a mathematical model. From a number of previous studies [9; 10; 11; 12; 13], the hierarchical model of fuzzy systems in evaluation applications turned out to be effective; therefore, it was used in the present research. Thanks to the hierarchical structure, the evaluation process can be defined as a modular construction. This increases the transparency and makes the whole procedure more flexible and easier to extend with new parameters or to change the existing ones, depending on the availability of research. Designing the individual life quality evaluation procedure, we focus on three different contexts of personal life aspects:  
* general opinion about one's own well-being and satisfaction;
* physical condition--physical everyday issues;
* satisfaction with work and its results. If there is no reason to emphasize any area of life, in the reliable quality evaluation model, we treat all partial assessments as equally important. In the study, the Perceived Stress Score (PSS10), Maslach Burnout Inventory (MBI), and Nordic Musculoskeletal Questionnaire (NMQ) were used. PSS10 measures psychological stress--it is used to assess the extent to which situations in a person's life are judged by them to be stressful [14]. MBI is a tool to measure professional burnout in three dimensions: emotional exhaustion (EE), depersonalization (DP), and personal achievement (PA) [15]. The Satisfaction with Life Scale (SWLS) is a short 5-item instrument designed to measure global cognitive judgments of satisfaction with one's life. The NMQ is a symptom questionnaire for musculoskeletal disorders, mainly for lower back, neck, and shoulder pain [16]. All of the above-mentionedtests are frequently used, valid, and reliable [17; 18; 19] and thus comparative material is more readily available, but they are rarely used simultaneously, which adds value to the present study. We were particularly interested in the influence of the COVID-19 pandemic onwell-being and life satisfaction, taking into consideration also the possible effects of burnout and occupational stress. Occupational burnout is a multidimensional syndrome that includes emotional exhaustion, depersonalization, and a low sense of fulfillment at work. A literature review of the impact of the COVID-19 pandemic on life satisfaction, conducted on five leading bibliographic databases, showed 354 papers published between 2020 and 2022 (56 in 2020, 195 in 2021, and 146 in 2022), focusing mainly on socioeconomic disparities. Only one of them used computational intelligence. A similar literature review of the impact of the COVID-19 pandemic on burnout, conducted on five leading bibliographic databases, showed 1567 papers published between 2020 and 2022 (393 in 2020, 948 in 2021, and 386 in 2022), including 111 reviews (35 in 2020, 65 in 2021, and 23 in 2022) and only 19 meta-analyses (5 in 2020, 8 in 2021, and 2 in 2022). As many as 212 papers were concerned with building some form of model of the impact of the pandemic on occupational burnout, but none used a computational model for this purpose, significantly speeding up the analysis and allowing much broader inferences from the data.