Mathematical Model Building for COVID-19 Diseases Data in European Countries Maksym Zaliskyi a , Roman Odarchenko a, b , Yuliia Petrova a , Maksim Iavich c and Irakli Pirtskhalava d a National Aviation University, Lubomyr Huzar Ave., 1, Kyiv, 03058, Ukraine b Yessenov University, Aktau, Kazakhstan c Caucasus University, Tbilisi, Georgia d Scientific Cyber Security Association (SCSA), Tbilisi, Georgia Abstract The paper deals with the problem of mathematical model building for COVID-19 diseases data. The literature analysis showed that a number of models already exist for these purposes. In this paper, the authors pay attention to the use of regression analysis methods to describe statistical data. For data on new cases of diseases in Ukraine, Poland and Italy, a comparative analysis of the use of regression models based on polynomials of the 5th, 7th and 10th order, mathematical model building in a sliding window, as well as a segmented regression model was carried out. During the use of the segmented regression model, additional optimization of the switching point abscissa was performed. The choice of the best model was performed according to the criterion of the minimum standard deviation. The research results can be used in process of solving the problems of predicting the spread of COVID-19 in the different countries. Keywords 1 Statistical data processing, regression analysis, model building, COVID-19. 1. Introduction In December 2019, there was an outbreak of pneumonia in Wuhan 2019 – 2020, as a result of which the COVID-19 virus strain was detected for the first time. By the first ten days of June 2020, the pandemic had affected 188 countries, more than 7 cases of infection were detected in the world and 411,000 people died. Now we have more than 37 million cases of infection, more than 1 million people died and more than 28 million people already recovered (Table 1). The COVID-19 pandemic completely changed our life. It is profoundly affecting how people engage with one another across industries and geographies. Physical distancing and other quarantine measures have shifted activities once considered critical to have in person to digital and remote channels. Despite the quarantine measures and the fact that the peak of coronavirus cases passed in the world (in accordance with statistical prediction), a decreasing the number of detected cases has not been observed for a sufficiently long period [1]. Ukraine occupies the 25-th position in total country list, but recently there is a significant increasing the COVID-19 total cases and new deaths in our country. It’s very important to build mathematical models for COVID-19 spreading and these models must be adequate and powerful. IDDM’2020: 3rd International Conference on Informatics & Data -Driven Medicine, November 19–21, 2020, Växjö, Sweden EMAIL: maximus2812@ukr.net (M. Zaliskyi); odarchenko.r.s@ukr.net (R. Odarchenko); panijulia.p@gmail.com (Yu. Petrova); miavich@cu.edu.ge (M. Iavich); irakli.pircxalava@yahoo.com (I. Pirtskhalava) ORCID: 0000-0002-1535-4384 (M. Zaliskyi); 0000-0002-7130-1375 (R. Odarchenko); 0000-0002-3768-7921 (Yu. Petrova); 0000-0002- 3109-7971 (M. Iavich); 0000-0002-7017-9144 (I. Pirtskhalava) © 2020 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0). CEUR Workshop Proceedings (CEUR-WS.org)