3. Secondary data analysis
This section will present a summary of the analysis conducted on the available secondary data. The original study by Van der Meer et al. [1] was based on data for the period 1995–1999; the present study uses data for the period 1995–2004. We explore the data through contingency tables, which can then form the basis for an empirical BBN. In Section 3.2, we shall provide a discussion of the shortcomings of the data and the implications for inference.
3.1. Analysis of secondary data
This study is an investigation into the statistically significant factors that influence the ratio of lives saved to lives lost (relating to the SAR incidents in a given Coastguard district in a given year), which we will simply refer to as the ratio. We note that the ratio is a monotonic transformation of the probability of a life being saved given that the person involved is in a life-threatening situation and, as such, the inference we derive is equally applicable to both metrics.
The performance of districts with respect to the ratio varies considerably from district to district. Fig. 1 is a boxplot describing the distribution of the ratio between 1995 and 2004 for each UK Coastguard district. We investigate the characteristics of these districts to determine if there is a systematic difference due to some explanatory factors, such as staff workload, average size of incidents or length of coastline monitored.