## 5 Conclusions  
This study analyzed the difference in the frequency of fatal incidents and the probability of fatal incidents in different construction work types. The purpose of this research was to identify the level of construction risk by analyzing the frequency of fatal incidents and the fatality rate using an integrated time series with estimation method. The hypothesis test was performed through statistical analysis to identify the differences between types of construction work. Finally, the degree of risk related to accident types and types of construction work were analyzed. This research was processed in five stages: first, 4337 fatal incidents at construction work sites from 2007 to 2016 were collected. Moreover, the yearly revenue from construction work, workers' daily wages, and ratio of the labor cost to revenue were surveyed to calculate the fatality rate. Second, the construction work was categorized by 27 types, and accident type was categorized by 18 cases, respectively, considering related laws and previous research. Third, because the frequency of fatal incidents featured an uncertainty problem, it was difficult to analyze the fatal incidents with complete accuracy. Therefore, the estimated frequency of fatal incidents was suggested to solve this problem as the frequency of fatal incidents using combined exponential smoothing and Monte Carlo simulation. Forth, the fatality rate was presented by fatality rate and calculated by considering yearly revenue from construction work, workers' daily wages, and the ratio of the labor cost to revenue. Fifth, the hypothesis test was carried out to identify the difference between 27 construction work types from the viewpoint of the frequency of fatal incidents and the fatality rates. The results of this research were as follows. First, regarding the aspect of the frequency of fatal incidents,'reinforced concrete construction work' had the largest fatal incidents as a type of construction work for 10 years with 66.5 fatal incidents per year. Second, the top fatality rate in construction work types was'scaffold and demolition work' which was suggested by 28.65\(\%_{\rm{cc}}\). Through the comparison between the frequency of fatal incidents and fatality rates, the difference in the degree of risk could be identified. Third, the difference among types of construction work was identified by using a hypothesis test. [PERSON]'s test resulted in \(p\) = 0.000 (\(p\)-value \(<\) 0.05) and it had statistical significance. Finally, the degree of risk of accident type in each type of construction work was analyzed. The most significant accident type was 'fall', which occurred in 2515 fatal incidents (57.99\(\%\)) and 2.33\(\%_{\rm{cc}}\). However, the most dangerous accident type and its probability differed in the type of construction work. For instance, the accident type 'collision' was the highest in the 'earth work' type at 85 fatal incidents and a 0.56\(\%_{\rm{cc}}\) fatality rate. The contributions are as follows: (i) from the viewpoint of the research aspect, since the number of fatal accidents varied from year to year, the frequency of fatal incidents had an uncertainty problem. Therefore, it is difficult to predict the frequency of fatal incidents in the future. Thus, to address this problem, this research employed an integrated time series and estimation method which has a predictive aspect that is beneficial in resolving the uncertainty problem. It was possible to predict the number of fatal incidents without the uncertainty problem using 10-year historical data for 27 work types. (ii) From the viewpoint of the technical aspect, the difference in the degree of risk for 27 work types and 18 accident types was identified on the basis of the frequency of fatal incidents and fatality rates. Several previous studies mainly focused on specific construction work types or accident types, however, this study considered all construction work types within the general category of building and civil construction.