## 2 Materials and Methods
### Relevance and Significance Evaluation Criteria  
Evaluating the relevance and significance of primary articles is crucial for minimizing biases and maximizing the internal and external validity of research [25]. Following this premise, and with the aim of maintaining scientific rigor in the investigation, the relevance and significance of the selected primary studies were assessed using an adaptation of the instrument proposed by Kitchenham & Charters [25], [PERSON] et al. [28], and the categories proposed by [PERSON] [29]. Six criteria were defined and grouped into three categories described below (the six criteria in question format are presented in Table 4, where the related category for each criterion can also be found):  
* Content Relevance: This category evaluates the study's pertinence in relation to the research topic and its theoretical or practical contribution to the field of study. It focuses on how clearly the study addresses specific aspects of the investigated topic and how these aspects are relevant to the academic or professional community [30; 31].
* Scientific Rigor and Validity: This category assesses the methodological soundness of the study and the validity of its results. It emphasizes the rigor of the research design, the appropriateness of the methods used, and the clarity in presenting the results, including how the study's proposal is validated [30; 32].
* Academic Impact and Recognition: This category evaluates the study's impact within the academic community and its recognition in the field. This includes the quality of the publication (measured through indexes such as Scimago quartiles and CORE rankings) and how frequently the study has been cited by other researchers [33; 34].
* Additionally, to assess the quality of the selected studies, a questionnaire was designed with a scoring system of three values: (\(-1\)) the study does not address the research questions posed, (0) the study partially addresses each research question, (+1) the study explicitly answers the research questions, based on the evaluation artifact proposed by [PERSON] et al. [25].  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Category**} & \multirow{2}{*}{**Id.**} & \multicolumn{3}{c}{**Scoring for Responses**} \\ \cline{3-6}  & & **Criteria** & **+1** & **0** & \(-1\) \\ \hline \multirow{4}{*}{Content Relevance} & \multirow{4}{*}{1} & The study clearly addresses SD in the development of agile software projects from the perspective of happiness and/or unhappiness in agile software development communities. & Yes & Partially & No \\  & & & & & \\ \cline{2-6}  & & The study proposes a set of elements to identify and mitigate unhappiness in agile software development communities. & Yes & Partially & No \\ \cline{2-6}  & & & & & \\ \cline{2-6}  & & The study validates the presented proposal. & Through a case study & Through a focus group & Not validated \\ \cline{2-6}  & & & & & \\ \cline{2-6}  & & The study clearly presents the results obtained after applying the presented proposal. & Yes & Partially & No \\ \hline \multirow{4}{*}{Academic Impact and Recognition} & \multirow{4}{*}{5} & The study has been published in a relevant journal, conference, or congress. The Scimago quartile rankings & Highly relevant (Q1 and Q3 for journals and A or B for unranked for conferences) & Relevant (Q2 and A for congresses) & Not relevant (Q4 for congresses) & Right relevant (Q2 and A for congresses) & Right (Q4 for congresses) \\  & & & & & \\ \cline{1-1} \cline{2-6}  & & The study has been cited by other authors. & & Cited by one to five authors & Not cited \\ \hline \hline \end{tabular}
\end{table}
Table 4: Criteria for evaluating the quality of primary studies.