# Systematic Literature Review on Test Case Selection and Prioritization: A Tertiary Study
## 4 Results and Analysis
### RQ4. How Can the Quality of Secondary Studies Be Compared? The categorization presented for various TCS&P techniques in the secondary studies was recorded and is plotted in Figure 15. The highest percentage of studies categorize the techniques based on the approach, whereas a few studies specifically chose genetic algorithms (GA), and 27% of the studies chose other unique categorization techniques. Figure 14: Domain of the tools used. Figure 13: Tools mentioned in secondary studies. The categorization trend can be justified by the evident change in the upcoming techniques over time. In addition to this, a few studies focused on a specific area of TCS&P rather than on the general analysis of TCS&P. Therefore, categorization is not sufficient for quality assessment. **RQ 4.1:**_How have the research questions been used in the secondary studies?_  
The different approaches used in secondary studies clearly highlight the importance of research questions when performing a secondary study. Hence, the research questions (RQs) covered by secondary studies in TCS&P were analyzed. Figure 16 represents the number of RQs considered by the studies. Most of the studies mentioned between three and five RQs. The count of RQs includes the sub-questions of the RQs, as mentioned in the study. Publication trends determine the most found RQs. The majority of the secondary studies included RQs that are factual in nature. Only five studies analyzed the collected facts and discussed their findings from the analysis. No peculiar trend could be seen in terms of increasing RQs or in the improvement in the quality of RQ. Figure 16: Number of research questions in the 22 studies for the survey. Figure 15: Categorization criteria chosen by secondary studies. Figure 17 shows that 63 % of the surveys in TCS&P focused on illuminating the 'facts' of working in the area. Only 23% of the secondary studies also focused on the analysis part of the work accomplished in the area. This highlights the deficit in analytically surveying or reviewing the TCS&P field over time. This also motivated us to propose detailed analytical RQs as much as possible within the logical technical constraints and limitations of time and cost. Figure 18 indicates that the majority (77%) of the surveys clearly and substantially answered the defined RQs. The remainder of the surveys either lack a pre-defined objective for the study or did not substantially answer the defined RQs. Although 23% of the studies did not answer their RQs, it is relevant to highlight the importance of proper usage of RQs in secondary studies. **RQ 4.2:**_What is the quality of the secondary studies performed in the area?_  
We worked with a total of seven Research Paper Quality (RPQ) parameters in order to provide a qualitative analysis of the secondary studies published in the area of regression TCS&P. These RPQs were designed to derive their inspiration from seminal studies [20; 21] in the area of TCS&P. Table 8 lists the RPQ values allocated to the 22 surveyed studies during research and analysis. Figure 17: Quality of research questions considered in the 22 studies for the survey. RPQ1 (RQ) denotes whether the study mentions and answers the RQ or not. A study was assigned the value '1' if it was found to mention the RQs; else, it was assigned the value '0'. RPQ2 (RQ Quality) represents the quality of the RQ research in the secondary study. Value '0' means that no research questions appeared in the secondary study, so they were not answered. Secondary studies having RQs framed to provide only descriptive analysis of the existing data, without providing exploratory, inferential, predictive, or diagnostic analysis of the primary studies, were assigned the value '0.5'. Value '1' means high-quality RQs were specified and answered. RPQ3 (Future Prospects): A study that mentions the scope of future prospects or gives directions to contribute further to the area received the value of '1' whereas value '0' was assigned to the remainder.