Figure 4
From: Acquired bloodstream infection in the intensive care unit: incidence and attributable mortality
Plot of scaled Schoenfeld residuals versus transformed time (based on Kaplan-Meir estimate of survival function) demonstrating acceptable linearity for the proportional hazard for the covariate Acquired BSI. Beta(t) is the exponential associated with the covariate, equivalent to the natural logarithm of the hazard ratio. The solid black line is a smoothing-spline fit to the plot, with the broken lines representing a ± 2-standard-error band around the fit. Grey line represents a completely proportional (time-invariant) hazard ratio of 2.89. BSI, bloodstream Infection.