*4.1. Summary of Results*

Table 1 shows the results for the Fisher's exact tests comparing accidents with maintenance contributions to all accidents in the ICAO official accident data set. The characteristics that are statistically significant include region of occurrence (ROc), phase of flight (PoF), occurrence categories (OC), and manufacturer (Manu). The characteristics which were not statistically significant are the fatalness (Fat), region of operator (ROp), maximum takeoff mass (Mass), engine types (ET), and number of engines (nE). Table 2 shows the Fisher's exact test results for those characteristics which were tested against a uniform expected distribution. Here, all but the operator's business model (BM) were statistically significant; including, maintenance issue (MI), system/componen<sup>t</sup> issue (SC), the type of operation (Op), and the age of the aircraft at the time of the accident in decades (Age). Each of these characteristics will be discussed further below.

**Table 1.** Fisher's exact test, comparing characteristics of accidents with maintenance contributions to all accidents, in the ICAO official accident data set.


**Table 2.** Fisher's exact test, to determine if characteristics of accidents with maintenance contributions are different to an expected uniform distribution.

