## 2 Materials and Methods  
For this case study, data were collected from two important companies from Romania, named Company A and Company B to protect their names/brands, as follows:  
* For company A, there were 215 registrations between April 2018 and December 2020;
* For company B, there were 734 registrations between July 2020 and January 2023. In addition, economic indicators were collected from a national internet page (www.listafirme.ro) (accessed on 30 January 2023) [23]. The variables used in the study are both categorical and continuous, mentioning for each categorical variable the codification used by the authors for the statistical software SPSS 23.0 (this step is necessary for statistical analysis of all the variables as nominal and/or ordinal express in words and to facilitate the applications of statistical methods through the specific software) as follows:
* Categorical variables (expressed by words, namely also qualitative/\"dummy\" variables):
* The month of proposal, the planned month for implementing, and the effective implementation month of change requests were assigned the following SPSS codes: 1, January; 2, February; \(\ldots\); 12, December. * The year of proposal, the year for implementing, and the year of effective implementation of change requests were assigned the following SPSS codes: 1, 2018; 2, 2019; 3, 2020; 4, 2021; 5, 2022; 6, 2023. * The change request statuses were assigned the following SPSS codes: 10, preparation; 11, canceled; 20, manager approval; 22, planning phase; 24, validation phase; 30, start implementation; 40, local confirmation for implementation; 44, global confirmation for implementation; 48, closed. * The types of processes proposed for change were assigned the following SPSS codes: 1, engineering change and 2, correction. * The number of days from creation to planning of change requests and the number of days from planning to effective implementation of change requests were assigned the following SPSS codes: 1, <10 days; 2, 11-20 days; 3, 21-30 days; 4, 31-50 days; 5, 51-100 days; 6, 101-200 days; 7, 201-300 days; 8, >300 days. * Customer involvement in a change request was assigned the following SPSS codes: 1, yes or 2, no. * Continuous variables (expressed by numbers, namely also quantitative/numerical variables) for all the economic indicators for the last five years, i.e., 2017-2021, were as follows: turnover, net profit, own capital, number of employees, debts, and fixed assets (all of these indicators in Romanian lei). Table 1 presents some details regarding the companies included in the research. Table 2 lists the economic indicators of performance for the last five years for each company and practically all the continuous/numerical variables from the study are presented for a better visualization of similarities and differences of these companies. All the data were transformed into current prices and are expressed in Romanian lei, for a correct dynamic analysis from an economic point of view. Because this research is based on big data collected from two automotive companies, complex statistical methods were applied according to the type of data, i.e., qualitative/categorical and/or continuous/numerical data. First, descriptive statistics were calculated by using the statistical software SPSS 23.0, then the normal distribution of the numerical data was tested with the aim to choose which statistical method would be applied. In this section, we present a short description of the chosen and applied statistical methods. Descriptive statistics were calculated for each economic indicator, and the results were presented classically as mean \(\pm\) standard deviation (minimum value \(-\) maximum value) for each continuous variable mentioned in Table 2 and as absolute and relative frequencies for categorical/\"dummy\" variables, separately for each company. To test if there were statistically significant differences between whether or not customers are implicated in the change process with respect to change request status, a chi-square bivariate test was applied.