Detailed Results
Statistical Findings
War Period Analysis
Key Finding: U-Boats commissioned during WWII had significantly shorter lifespans than interwar vessels.
- Interwar U-Boats: Median survival ~800 days
- WWII U-Boats: Median survival ~400 days
- Statistical Significance: p < 0.001 (log-rank test)
U-Boat Type Comparison
Key Finding: Type VIIC submarines showed superior survival rates.
| Type | Sample Size | Median Survival (days) | 25th Percentile | 75th Percentile |
|---|---|---|---|---|
| VIIC | 568 | 445 | 189 | 894 |
| IXC | 174 | 412 | 165 | 823 |
| VII | 87 | 401 | 178 | 756 |
| VIIB | 24 | 389 | 167 | 712 |
| IXB | 14 | 356 | 145 | 634 |
Commander Effect Analysis
Key Finding: Notable commanders significantly improved U-Boat survival.
- With Notable Commander: Median survival 900 days
- Without Notable Commander: Median survival 500 days
- Hazard Ratio: 0.65 (95% CI: 0.58-0.73)
- Interpretation: 35% reduction in risk of loss with notable commander
Survival Curves
By War Period
The survival curves clearly demonstrate the harsh reality of WWII operations, with steep initial drops in survival probability.
By U-Boat Type
Despite different designs and capabilities, most U-Boat types showed remarkably similar survival patterns.
By Commander Status
The most dramatic difference in survival curves, highlighting the critical importance of experienced leadership.
Cox Proportional Hazards Model Results
Coefficients:
coef exp(coef) se(coef) z p
type_VIIC -0.234 0.791 0.089 -2.63 0.009
war_period_WWII 0.892 2.441 0.156 5.72 <0.001
notable_cmd_yes -0.431 0.650 0.061 -7.07 <0.001
Concordance: 0.72
Likelihood ratio test: 156.3 on 3 df, p < 2e-16
Model Interpretation:
- Type VIIC reduced hazard by 21% compared to baseline
- WWII commissioning increased hazard by 144%
- Notable commanders reduced hazard by 35%
Time-Varying Effects
Analysis revealed that the commander effect was most pronounced in the first 500 days of service, suggesting early operational experience was critical for long-term survival.