# The Gap between the Admitted and the Measured Technical Debt: An Empirical Study
## 5 Mismatch Identification  
Here, we present our findings based on the implemented research method and the empirical results. To answer the research questions, let us present our investigation on the mismatches, the differences between measured and admitted technical debt, and the possible causes that lay behind them. The results (see Figure 2) imply deviations not only when we compare the self-admitted technical debt (SATD) to the measured one but also when we consider the measured technical debt with two different tools. The pattern is hard to spot, since in some cases (#1, #3, #6, #13, #14), the measurements are aligned, while in others (#6, #9, #10), the SonarQube measurement is aligned well with SATD, but only in 1 case (#6) are both measurements and the SATD aligned well. Since the differences are shown clearly in the results, we prepared their analysis. * Firstly, the sizes of the technical debts were **compared in a relative manner**. Please note that, although the mismatch in Figure 2 seems substantial, their absolute values, normalised to project effort, are not. For example, in the case of project #3, the reported SATD is 11.7%, while the measured values are 7.6% and 7.9%. This is why the difference is 4.1% and 3.8%, which represents approximately 2 working days difference in the reported technical debt amount for a project with a 4 person-month development effort. * Secondly, **the absolute technical debt values were compared** in terms of the differences between them; e.g., for project #2, SonarQube reported 1.6 h (1%) and Vector Squore reported 4.5 h (2.8%)--a factor of 2.8 higher than the SonarQube measurement. The complete analysis of all combinations is shown in Table 4, including the following:  
* The relative difference between SonarQube and Vector Squore per project;
* The relative difference between SonarQube and the SATD per project;
* The relative difference between Vector Squore and the SATD per project;
* The difference factor between SonarQube and Vector Squore per project;
* The difference factor between SonarQube and the SATD per project;
* The difference factor between Vector Squore and the SATD per project. In Table 4 the first three columns focus on the relative difference, while the second three columns show the difference factor between the technical debt amounts for the particular project. Please note that a value of _\"0\"_ is the best (i.e., _\"no difference\"_) for the relative difference, and the value _\"1.0\"_ is the best (i.e., _\"no difference\"_) for the difference factor. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Product** & **SonarQube** & **Square** & **SATD** \\ \hline \#1 & A & A & B \\ \#2 & A & A & A \\ \hline \#3 & B & B & C \\ \#4 & A & B & C \\ \#5 & A & A & B \\ \hline \#6 & B & B & A \\ \hline \#7 & B & A & A \\ \hline \#8 & B & B & A \\ \hline \#9 & B & A & B \\ \hline \#10 & C & A & C \\ \hline \#11 & A & A & B \\ \hline \#12 & A & B & B \\ \hline \#13 & B & A & A \\ \hline \#14 & A & A & B \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Technical debt SQALE rating per product. The table demonstrates a low number of _\"no difference\"_ or _\"close-to-no difference\"_ values, and it does, surprisingly, demonstrate some high deviations. Let us discuss the statistics. As the analysis shows clearly, the mismatch between the technical debt amount, measured with the SonarQube, is **significantly different** (\(p=0.037\)) to the SATD. This is extremely well demonstrated in the case of project #1, where we can observe that the SATD is 13.9 times higher than the debt measured by the SonarQube. Project #11 also shows the SATD having an amount five times that of the SonarQube measurement. The **significant difference** between the SATD and the measurement is also demonstrated clearly in the case of Vector Square (\(p=0.015\)). The SATD is over 10 times higher than the Square measurement in the case of projects #1, #10, and #11.