NRI involves comparing the reclassification tables of two models: the baseline model and the new model. It is typically broken down into two components: 1. Event NRI (NRIevent): This measures the correct reclassification of individuals who experience the event (e.g., a disease or condition). 2. Non-event NRI (NRInon-event): This measures the correct reclassification of individuals who do not experience the event.
The formula for NRI is as follows: \[ \text{NRI} = (\text{Proportion of correctly reclassified events}) + (\text{Proportion of correctly reclassified non-events}) \]
