# Drowning Risk Analysis Comparing Surf Bather Subgroups
## 3 Results
### Comparisons within Subgroups  
For gender, Table 3 shows that males had a lower contribution to drowning risk from the included factors but far higher crude exposure to water than females. This resulted in a male to female derived drowning ratio of 3.71:1 (Table 4). This ratio antecedent was below the specific drowning rate antecedent (6.11) but _just_ within the specific drowning rate antecedent 95% CI (see worked example at Appendix B). By age group, bathers <30 years had both higher drowning risk contribution from the included factors and higher crude water time exposure. This was reflected in a derived drowning ratio of <30 years to \(\geq\)30 years of 1.78:1 (Table 4). The ratio antecedent was higher than that found for the specific drowning rate (0.44) and outside the antecedent 95% CI. By age and gender subgroups, males \(\geq\)30 years had the lowest contribution to drowning risk from the included factors with the highest for females \(\geq\)30 years. The younger \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Bather Subgroup Drowning Risk** & **Derived** & **Specific Drowning Rate b** & **Specific Drowning Rate** \\
**Comparison** & **Drowning Ratio a** & **Specific Drowning Rate b** & **Antecedent 95\% CI** \\ \hline Males:Females & 3.71:1.00 & 6.11:1.00 & _3.71 to 10.11_ \\ \hline \textless{}30 years:\textgreater{}30 years & 1.78:1.00 & 0.44:1.00 & _0.30 to 0.64_ \\ \hline Males \textless{}30 years:Females \textgreater{}30 years & 12.18:1.00 & 2.50:1.00 & _1.35 to 4.63_ \\ Males \textgreater{}30 years:Females \textgreater{}30 years & 8.33:1.00 & 5.34:1.00 & _3.03 to 9.55_ \\ Females \textless{}30 years:Females \textgreater{}30 years & 4.50:1.00 & 0.29:1.00 & _0.09 to 0.84_ \\ \hline Surf:Swim or wade & 1.45:1.00 & 0.18:1.00 & _0.11 to 0.30_ \\ Surf:Swim & 3.28:1.00 & 0.18:1.00 & _0.11 to 0.30_ \\ \hline Male swim:Female swim & 3.02:1.00 & 5.35:1.00 & _3.19 to 9.03_ \\ Male surf:Female surf & 11.45:1.00 & 19.00:1.00 & _2.93 to 9.99_ \\ \hline Swim \textless{}30 years:Swim \textgreater{}30 years & 2.24:1.00 & 0.38:1.00 & _0.25 to 0.58_ \\ Surf \textless{}30 years:Surf \textgreater{}30 years & 1.48:1.00 & 0.82:1.00 & _0.35 to 1.92_ \\ \hline \hline \end{tabular} Note. a derived from study data. b derived from mortality data.  
\end{table} 
Table 4: Risk analysis drowning ratios and drowning rates. Figure 3: Comparisons of risk analysis drowning ratios and specific drowning rates. male subgroup had the highest crude water exposure time, with the older female subgroup lowest. This latter subgroup was used as the consequent base for ratios and rates which provided for comparisons among all four gender-age subgroups. The derived drowning ratio antecedent was highest for the younger male subgroup, followed by the older male subgroup and then the younger female subgroup (Table 4). In contrast, the comparative specific drowning rate antecedent was highest for the older male subgroup, followed by the younger male subgroup, then the older female subgroup. The antecedent for males \(\geq\)30 years versus females \(\geq\)30 years (8.33) was the only comparison among the above three to fall within the specific drowning rate antecedent 95% CI. By activity, surfers had lower contributed drowning risk from included factors than both combined waders and swimmers and swimmers only. Surfers had higher crude water time exposure compared to both subgroups. For both comparisons, surfers had a relatively higher derived drowning ratio (1.45:1 and 3.28:1, respectively; Table 4) but a lower specific drowning rate (0.18:1). Both ratio antecedents were above the specific drowning rate antecedent 95% CI. For activity by gender, the surfer grouping results somewhat mirrored gender only differences (Table 3) but at a comparatively higher ratio (11.45:1) and rate (19.00:1; Table 4). For this comparison, the derived drowning ratio antecedent fell within the specific drowning rate antecedent 95% CI, although due to the small sample size and high proportion of male surfers, the specified range was large.