1. Introduction
2. Data Processing and Sample Selection
3. Analysis
4. Results
4.1. Sample Luminosity-Temperature Relation
4.2. Selection Function
4.3. Likelihood
4.4. Inference of Model Parameters
4.5. The $L_{XXL}$ - T Relation
4.6. Posterior Predictive Checks
4.7. The $L_{bol}$ - T Relation
5. Discussion
5.1. Comparison with Other Observational Studies
5.2. Impact of Cool Cores
5.3. Systematic Effects
5.4. Do the Data Require γ LT as a Free Parameter?
5.5. Interpreting γ LT
5.6. Comparisons with Simulations
6. Conclusions