## 3 Proposed Research Methodology  
Every occupational accident is caused by at least several causes. For the purpose of the conducted research, the definition of a cause of an accident was assumed as all deficiencies and irregularities related to: employees and their abnormal behavior, material factors, general organization of work, and the organization of a workplace. For the purpose of the developed methodology, the classification proposed by the European Statistical Office of the European Union EUROSTAT was assumed, which distinguishes eight subgroups of causes of occupational accidents, namely: \(P_{1}\)--the inappropriate state of the material factor; \(P_{2}\)--the inappropriate general organization of work; \(P_{3}\)--the inappropriate organization of a workplace; \(P_{4}\)--the lack of appropriate material factors or inappropriate use of these factors; \(P_{5}\)--the lack of using protective equipment by an employee; \(P_{6}\)--inappropriate unlawful employee behavior; \(P_{7}\)--the psychophysical condition of an employee that does not enable safe work to be carried out; \(P_{8}\)--inappropriate employee behavior. The set of causes of occupational accidents can be written as  
\[P=\{P_{g}:g=1,\ \ldots,8\} \tag{1}\]  
where \(P\)--the set of causes identified in the analysed accidents, \(P_{g}\)--a subgroup of causes (\(g=1,\ \ldots,8\)). Moreover, the so-called TOH method [21] was adopted and is one of the most commonly used classifications of causes of accidents in the assessment of occupational accidents. It assumes that each accident is the result of three types of causes: technical (\(T\)), organizational (\(O\)), and human (\(H\)). Therefore, the set \(P\) of all causes of occupational accidents is the sum of the subset \(T\) representing the technical causes, subset \(O\) involving the organizational causes and subset \(H\) constituting the human causes. \[P=T\cup O\cup H \tag{2}\]Technical, organizational, and human causes involve the causes of the following subgroups  
\[T=\{P_{g}:g=1\}\quad O=\{P_{g}:g=2,3\}\quad H=\{P_{g}:g=4,\ \ldots,8\} \tag{3}\]  
In addition, in each of these \(T,O,H\) sets, several or more specific causes are listed  
\[T=\{t_{k}:k=1,\ \ldots,K\}\quad O=\{o_{m}:m=1,\ \ldots,M\}\quad H=\{h_{n}:n=1,\ \ldots,N\} \tag{4}\]  
where \(t_{k}\)--a detailed cause in set \(T\), \((k=1,\ \ldots,K)\), \(o_{m}\)--a detailed cause in set \(O\), \((m=1,\ \ldots,M)\), \(h_{n}\)--a detailed cause in set \(H\), \((n=1,\ \ldots,N)\). Each cause identified during the assessment of an accident is eligible for an appropriate subset of detailed causes: \(t_{k}\ (k=1,\ \ldots,K)\) or \(o_{m}\ (m=1,\ \ldots,M)\) or \(h_{n}\ (n=1,\ \ldots,N)\). The scheme of the classification of causes of accidents according to the TOH method is shown in Figure 1.  
It is proposed to adopt the TOH methodology as a benchmark for classifying the direct causes of accidents at workplaces that use building scaffolding. The causes of accidents, which were identified in the post-accident protocols, were classified to the three defined in the TOH method subset of causes (technical, \(T\); organizational, \(O\); and human, \(H\)). Pareto-Lorenz analysis and ABC classification are proposed to identify the causes with the greatest importance [22; 23]. The proposed calculation methodology is universal, which means that it applies to the analysis of each of the three groups of causes of accidents involving scaffolding (\(T\), \(O\), \(H\)). The procedure of the carried out analysis is as follows:  
* Defining specific detailed causes and their cardinalities in the analyzed generic group. This information can be presented as a sequence of ordered pairs of numbers \((p_{x},a_{x})\), where \(p_{x}\) (\(x\) = 1,..., \(X\)) (represents the identified detailed cause and \(a_{x}\) indicates the number of occurrences of the examined cause in the analysed subset \(T\), \(O\), or \(H\). * Organizing sequences of pairs of numbers \((p_{x},a_{x})\) that describe the analysed causes in a descending order.