# Tagged Questions

In survival analysis, the hazard rate at time $t$ is the instantaneous probability of death at $t$, conditional on survival until $t$.

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### Calculating standard error for a ratio of hazard ratios

I'm trying to calculate if there has been a change in risk over time, during 10 years of follow-up, for young adults to develop depression. I've successfully calculated the hazard ratio and 95% CI ...
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### How to calculate the probability of death between two discrete time periods using survival curves

I was hoping somebody could help, I am trying to work out the probability of death between two time points on a survival curve. i.e. I have my survival curve as follows (this is an example Kaplan-...
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### Determining reference groups in coxph

When I run a univariate cox regression test using the survival package in R, assuming that my categorical variable-factor has ...
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### Lee (1983) sample selection correction with accelerated failure time model (in Stata)

I am trying to replicate the selection control used by Henderson et al. (2006), which is derived from Lee (1983). Henderson et al study CEOs over time and try to control for the likelihood that a CEO ...
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### How to model time to event / survival analysis when event outcomes are not binary

My data set looks like this ...
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### What's the difference between univariate and multivariate cox regression?

I'm dealing with oncology patients so it would be nice to know whether to use univariate or multivariate cox regression. I have some books on survival analysis but they don't elaborate the academic ...
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### What imputation methods can be used for missing not at random covariate values in a survival analysis?

I'm new to survival analysis and trying to understand how to use it properly. My dataset is a time series dataset where most dependent variable values are available, 2 dependent variable values are ...
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### Hazard model for three-tiered-response dependent variable

My time-series dataset is composed of measurements for a number of independent variables and one dependent variable. The dependent variable accepts 3 responses: weak reaction, strong reaction, or no ...
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### Estimate the treatment effect in each level of a subgroup with Cox regression

People generate forest plots to determine the benefit of one treatment regimen over another through univariate hazard ratios. How do you generate them? Is there an R package that handles that? (This ...
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### Intuition behind Hazard Rate

I am confused about the equation definition of hazard rate. I get the idea of what the hazard rate is, but I just don't see how the equation expresses that intuition. If $x$ is a random variable ...
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### Time Series Shocks with Exponential Decay

Imagine a piano key played in an auditorium: The amplitude of the sound wave is perhaps highest in the first milliseconds, then slowly decays to zero if no other notes are played. If other notes are ...
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### Difference between survival and hazard

I am trying to find an intuitive explanation of the difference between the hazard and survival rates? Are the two the same thing but expressed differently?
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### How to get event hazard rates from a survfit object for sample size calculation

I want to calculate the sample size for a clinical trial (right-censored time to event data). I have data of a retrospective analysis and would like to use nSurv ...
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### Multilevel Model for time to event data

How can I write the general equation for multilevel parametric proportional hazard model and multilevel cox proportional hazard model?
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### The difference between average and marginal treatment effect

I have been reading some papers, and I am unclear about the specific definitions of Average Treatment Effect (ATE), and Marginal Treatment Effect (MTE). Are they the same? According to Austin... ...
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### How to interpret hazard ratios for time-segmented variables?

I'm constructing a Cox regression model where patients were randomised to treatment or placebo, and then had certain continuous covariates measured at multiple time points through the course of the ...
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### How to scale the Hazard Function?

Please help me understand this: Imagine one has a population of 30 subjects, and their failure times are described by the Weibull distribution with parameters i.e: $\alpha=1.9,\ \beta=1.3$. \...
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### Modelling retirement of employees by age where only data of very few years are available

We want to model the retirement of employees. We have data on a yearly base for about 20,000 employees by age and some other properties. There are two questions: Suitable Approach In most cases we ...
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### Non-proportional Weibull hazard model with heaviside functions

I am trying to model a non-constant (and non-linear) hazard ratio between two groups (Group A and Group B), assuming that the baseline hazard for one of the groups can be described with the Weibull ...