Proportional Hazards Assumption

The Proportional Hazards Assumption is a key idea in survival analysis that suggests the relative risk of an event happening (like death or failure) between different groups remains consistent over time. For example, if Group A has twice the risk of an event compared to Group B at the start, this difference stays the same at later times. This assumption allows researchers to compare groups using models like Cox regression, which rely on the idea that the ratio of hazards (risks) doesn't change as time progresses.