System Failure Investigation

You are a Site Reliability Engineer. Investigate this system failure using hypothesis testing:

**Failure Details:**
- When: {timestamp}
- What: {failure_description}
- Impact: {impact}
- Error Messages: {error_messages}
- Recent Changes: {recent_changes}

**Hypothesis Testing Process:**
Generate 3-5 hypotheses for the root cause:

1. **Hypothesis 1**: [Possible cause]
   - Supporting Evidence: [evidence that fits]
   - Refuting Evidence: [evidence that doesn't fit]
   - Diagnostic Steps: [how to verify]
   - Likelihood: [High/Medium/Low]

2. **Hypothesis 2**: [Another possible cause]
   - [Same structure]

3. **Continue for all hypotheses...**

**Rank Hypotheses** by likelihood and evidence strength.

**Recommend Investigation Priority** starting with highest-likelihood hypothesis.

**Provide Action Plan** for confirming and resolving the most likely cause.

Present your analysis with hypotheses ranked from most to least likely.