## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Support (\%)** & **Confidence (\%)** & **Lift** & **Score** & **D** \\ \hline
26.6\% & 92.5\% & 1.148 & 23,016 & 0 \\
20.1\% & 70,0\% & 1.351 & 17,418 & 100 \\
15.1\% & 52.5\% & 1.553 & 13,064 & 200 \\
7.9\% & 27.5\% & 1.318 & 6844 & 300 \\
3.6\% & 12.5\% & 1.241 & 3111 & 400 \\
2.2\% & 7.5\% & 0.948 & 1867 & 500 \\
0.7\% & 2.5\% & 0.434 & 622 & 600 \\
0.0\% & 0.0\% & 0 & 0 & 700 \\
0.0\% & 0.0\% & 0 & 0 & 800 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Parameters of the rule with Cr-E-J-L body calculated for several thresholds of delay. Therefore, the risk values (of the delay appearance being greater than a certain number of days) can be read from Figure 9. It is consistent with common sense. The greater the delay, the lower possibility of its occurrence. However, it must be emphasized that the content of Figure 9 is created based on real data. There is also another rule found based on the Cr-E-J-L body, and it has the same head. The confidences for these two rules are presented in Figure 10.  
Confidence is a discrete function, as the nominator and denominator (defining confidence) are discrete by nature. However, confidence can be calculated for the continuous threshold (time), but is useless for the cases from the construction industry. Despite that, the lines in Figure 10 are presented as continuous. The blue line based on A-E-K body is continuous for the whole domain presented in Figures 9 and 10. The orange one (based on the Cr-E-J-L body) has two breaks (discontinuities). For days ranging from 370 to 386 and from 495 to 524, as the lift calculated for these rules is below 1, the rules are useless. There are no cases supporting this rule being delayed for more than 533 days, so the orange line ends there. In order to read the risk of delay greater than a certain threshold (given in days) and if there is more than one body for the rules found (as in Figure 10), it is recommended to use the confidence of a higher 7-Score. The calculated 7-Scores are higher for the rules based on the A-E-K body (blue line), except for the range from day 159 to day 196, as presented in Figure 11.  
Figure 10: The confidences of the rules for A-E-K and CrEJL for different numbers of days as the threshold of the head (delay). This range is marked with black vertical lines in Figures 10 and 11. There, the rule with the other body (Cr-E-J-L) should be used (confidence read based on the orange line that has a higher 7-Score in this range). The traditional approach to a construction contract risk estimation is based on statistics and on experts' opinions. It requires the experience of experts gained before a new assessment. The proposed method omits involving human's opinions. It is purely based on data. The experience--that is, past construction contracts completed--is necessary, but the risk is calculated based on formulas, algorithms, and a set of data collected. The higher the experience, i.e., the more cases serving as a source data, the more reliable the risk estimation. This statement points to the possible weakness of the proposed method. Analysis based on small databases can produce unreliable risk estimation. The other limitation of the invented method is the necessity of basing the risk estimation on the information gathered from the construction contracts of a similar scope of works. Assessing the risk of a road construction contract based on several completed apartment buildings is irrelevant and improper. Thus, the method can be applied by specialized contractors or clients (e.g., in the road construction, as in the analyzed case). Thirdly, the new, analyzed contract may not meet the criteria of the predecessors of the rules found to be the most informative. Then, the risk assessment is not possible. Considering the limitations of the invented method, it can be stated that the traditional approach to risk assessment (also based on experts' opinions) and the invented method should be used complementarily.