Questions tagged [hazard]
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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43 views
Cox's Proportional Hazard coefficients clarification
I'd like a clarification about the Cox proportional hazard coefficients reported on this page. For example, doesn't the hazard ratio (HR) for gender in that ...
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2answers
36 views
Hazard function equality $T = \min(T_1, T_2, …, T_n)$ [closed]
Let $T_i, i = 1, ..., n$ be independent continuous random variables. Denote by $h_i(t)$ the corresponding hazard function of $T_i$. Let $T = \min(T_1, T_2, ..., T_n)$. Denote by $h_T(t)$ the ...
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Meta analysis: Pooling hazard ratios of continuous vs. dichotomous parameters?
I have a question regarding pooling hazard ratios derived through different means for a meta-analysis. Software: RevMan 5; Method: generic inverse variance (log hazard ratios).
My issue is that some ...
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1answer
18 views
Can the hazard function be defined on a continuous state
The hazard function is defined as the instantaneous failure rate or instantaneous hazard rate as $\Delta t$ tends to zero
$$
h(t)= \lim_{\Delta t \to 0} \frac{R(t)-R(t+\Delta t)}{\Delta t * R(t)}
$$
...
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0answers
12 views
Kernel Density Estimation of Hazard rate using R
How can we estimate the hazard rate using Kernel density estimation? For the time being I am simulating 1000 observations from exponential distribution, then estimate its hazard rate using gaussian ...
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0answers
15 views
Facilitating Comparisons - 1 SD difference
I came across a paper that mentions this in their statistical analysis:
To facilitate comparisons among variables, the hazard rate ratio (HRR) was calculated for a 1-SD difference for each of the ...
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0answers
24 views
Survival prediction
I want to estimate the hazard ratio for a case-control study, and I want to test how the value of a continuous covariate affects survival. Does the covariate have to be normally distributed?, that is ...
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13 views
The difference between the cumulative baseline hazard and the cumulative hazard?
I'm not sure what is the difference between the cumulative baseline hazard and the cumulative hazard?
Could you please explain it if you are an expert in this field?
Thanks
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17 views
Survival model building with time dependent covariates
I am looking to build a Cox proportional survival hazard model in SAS on time dependent covariates. Ultimately, I will put this model in production and score on recurring basis to target the right ...
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0answers
42 views
Cox hazard Model: HR of 1 variable greater than 1 in simple regression becomes smaller than 1 in a multiple regression
I'm performing a simple and multiple Cox regression. I have 1 dependent variable
$y$ and 10 independent variables:
$$X = x_1, x_2, x_3, x_4, x_5, x_6, x_7, x_8, x_9, x_{10}$$
A particularity of the ...
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1answer
62 views
Non-monotone hazard functions
I should start with the caveat that I am relatively new to Survival analysis. I was watching a Hulu documentary about Crocodiles last night, and they mentioned that baby crocodiles have a low chance ...
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0answers
18 views
What is the bandwidth in a hazard rate plot?
I am doing some Survival Analysis using SAS. On the Hazard Plots I noticed some values on each curve labeled "bw" which after some research, I assume it means bandwidth. However, after much searching, ...
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1answer
34 views
Interpretation of Cox Hazard Model with quadratic term
I am having trouble finding information on how to interpret coxph model hazard ratios with a quadratic term. Some of my variables are continuous count data, whereas others are continuous percentages.
...
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3answers
77 views
Extremely huge Hazard Ratios from Cox regression
We made a cox regression and ended up with huge HR for some of our variables. One of them (which was an interaction) gave us a HR=2747,093. Our dataset consists of only 74 observations. What is wrong?
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0answers
30 views
Finding the limit of a quotient of hazard functions
Let $\lambda_i(t),S_i(t)$ be the hazard and survival functions of two populations for $i=1,2$ and satisfy that: $\frac{S_2(t)}{1-S_2(t)}=\phi\frac{S_1(t)}{1-S_1(t)}$ (1) I want to proof that $\lim_{t\...
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Why is Stata smothed hazard estimate pruned to interval?
I have played through this R example to calculate hazard estimates.
I chased the whole thing through Stata and obtained a different graph, though.
R graph:
Stata graph:
What's the rationale ...
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1answer
94 views
Who invented the hazard function?
The hazard function or instantaneous failure rate is very popular in survival analysis:
https://en.wikipedia.org/wiki/Failure_rate
$$\lambda(t) = \dfrac{f(t)}{1-F(t)}.$$
However, I cannot find a ...
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1answer
184 views
How to interpret hazard ratios of Cox output?
I'm really struggling to understand how to interpret my R outputs in terms of hazards ratios. I have ran a Cox proportional hazard regression to compare survival between 2 treatment groups (neutron ...
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1answer
34 views
Survival model for an epidemic — can the observations be treated as independent?
I've been thinking about ways to tackle an epidemic modelling problem I've been working on, and I've come up against a conceptual difficulty over the way survival analysis works. Here's a really ...
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1answer
32 views
Interpret hazard ratio < 1
In my book the example for interpreting a hazard ratio < 1 includes just a single example with a hazard ratio of 0.5. It is very confusing. If you have a hazard ratio of 0.2, does that mean the ...
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0answers
20 views
was it the correct interpretation of hazard ratio by the authors of an article?
My question is not a pure statistics question but is a daily application of statistics and how we interpret the statistics result -
A study found that the hazard ratio (HR) of patients with high ...
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1answer
41 views
hazard ratio interpretation
Imagine that when we compare treatment A to treatment B (the group A is a high expression and group B is a low expression of gene X) and the pooled hazard ratio (group A in comparison to group B) is 0....
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2answers
361 views
Evaluating the hazard function when the CDF is close to 1?
I need to evaluate a hazard function $h(t;\theta) = \dfrac{f(t;\theta)}{1-F(t;\theta)}$, where $f$ and $F$ are a pdf and a cdf, respectively, at many values of $t$ (and for several values of the ...
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1answer
42 views
PCA Dimension Reduction for Cox Proportional Hazard Model
I am trying to figure out if it is possible and appropriate to use PCA to reduce the dimensions of my dataset? A little background - I have survival data with 8 covariates. I have run a Pearson's ...
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0answers
18 views
How to interpret the HR of morbidity when defined as time, not an event
I'm in need of guidance on how to interpret this hazard ratio: 3.3 HRs of cardiovascular disease morbidity when morbidity was defined as lag time from the date of entry until first relevant diagnosis ...
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1answer
91 views
Hazard function for a growing population
I want to model the expected failure rate in a growing population.
Each individual has a high infant mortality (e.g. Weibull(shape=0.5, scale=100)).
So the ...
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0answers
13 views
Hazard model for multiple streams of events
I've got multiple streams of events (suppose that only two) : for two countries we mark day by 1 if there is at least one new infection of rear disease, 0 otherwise, how to treat such dataset (2000 ...
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1answer
22 views
Is the assumption of risks proportionality required when we assessing the difference of two KM branches (curves)?
There are two KM branches (curves) (for example, for male and female). Can I use a log-rank test if the assumption of risk proportionality is not satisfied?
P.S. I checked this with the code: plot(Y~...
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1answer
286 views
Estimate the cumulative baseline hazard function from a Cox model coefficients
CoxPh model described as $h(t|X)=h_{0}(t)e^{\beta X}$ where $h_{0}(t)$ is the baseline hazard function and is non-parametric. If you have the following model,
...
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1answer
44 views
hazard rate linear function instead of hazard rate lambda( λ) [closed]
Can we find survival function from any hazard rate linear function? Lets say we do not have hazard rate of y as Lambda( λ) but we have hazard rate of y as a linear function. can we find the survival ...
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0answers
163 views
MLE estimation: Inverse gamma duration model with exogenous variables
I observe a cross section of durations, $t_1, \ldots, t_n$ which are all strictly positive and a corresponding vector of exogenous variables $x_i$ which are assumed not to change from time $T=0$ until ...
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1answer
22 views
Can I force the direction of hazards ratio?
I am doing a survival analysis using Cox's proportional hazards model with several predictive variables. Some of the estimated hazards ratio goes in an implausible direction, which contradicts what we ...
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1answer
110 views
Significant but very small beta coefficients in Cox proportional hazards calculation (survival analysis)
I'm analyzing TCGA data to investigate the effects of lncRNAs on survival. Among other things, I wanted to calculate a univariate CoxPH model for each gene to find genes whose expression levels have a ...
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0answers
60 views
interpretation of cox HR under non-proportional hazard
When the true hazard ratio $\lambda(t)$ is time varying as shown below, I used a standard cox regression to get a hazard ratio. If the hazard ratio of $\lambda=0.78$, how can this value be interpreted?...
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1answer
41 views
Why is Hazard Function called rate of failure?
I am confused why Hazard Function is called rate of failure. Here is what I understood about Hazard Function.
Suppose we are dealing with Weibull and let $f(X)$ be the pdf, $F(X)$ be the cdf.
Now, I ...
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0answers
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Estimation of standard errors in conditional discrete time logistic regression models
I'm estimating a conditional discrete time logistic regression model in STATA and predict hazard and survival functions after logit using predictnl
predictnl hazard= predict(pr), ci(hazard_lb1 ...
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0answers
8 views
Comparing two KM estimates outputs without raw data
Some raw data has gone missing, but I have the outputs of two KM curves - Both their survival estimates and patients at risk.
Is there any way for me to use just the estimates to test the difference ...
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0answers
42 views
Which duration model to use with a fully right censored database
Currently I'm examining the duration of residence of households. I have a database at my disposal that indicates how long a specific household resides in its current home. I want to explain their ...
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1answer
137 views
Piecewise exponential model - how to fit
I'm trying to go through the following paper: https://projecteuclid.org/download/pdf_1/euclid.aos/1176345693
it covers the piece wise exponential model for modelling hazard rates in a non-parametric ...
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0answers
229 views
Is Concordance index (C-index) only suitable for the cases that the failure rate increases with time?
According to my assumption, the C-index is "the fraction of pairs in the data, where the observation with the higher survival time has the higher probability of survival predicted by a survival model."...
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0answers
14 views
Understanding (dynamic) duration models
I have a general issue on how to properly use duration models to predict waiting times based on the (wide) class of Intensity models.
Let $t$ denote physical (calendar) time and denote the event-...
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0answers
25 views
Expected value of (F(x)/x(1-F(x)) where F(x) is CDF?
I was solving a problem and encountered the following:
\sum (f(x)/x) (F(x)/(1-F(x))
Here f(x) is pmf and F(x) is CDF. Is expected value of F(x)/x(1-F(x)) a known function? I found out that f(x)/(1-F(...
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0answers
32 views
How to combine three Date/time variables into one?
I'm applying a Cox-hazard model and i need some help on the time variable.
Let's say the context is reservations of a hotel room.
In my df, i have 3 date/time columns:
- Reservation date
- Arrival ...
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0answers
10 views
significance in relative hazard ratio
I am reading a paper where thy quote a relative hazard ratio (95% CI) as 4.61 (2.19-9.67) and report this as non significant, while another is 2.39 (1.16-4.93) which they report is significant.
Why ...
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2answers
134 views
Hazard function-Why is it not a pdf
I am trying to understand why the hazard function is not a PDF. For a random variable T, people often define the PDF of this random variable as:
$$f(t)=\lim_{\delta \to 0} \frac{P(t\leqslant T <t+...
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21 views
Weibull hazard Rate for Machine Vibration data
I have vibration measurements of machines over different duration till the Machine breaks down. I have several such records. How do I fit a Weibull model and compute the hazard rate. Is it that for ...
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1answer
248 views
Does centring the baseline hazard and linear predictor after cox regression alter confidence interval size around the cumulative hazard and risk score
I am trying to derive risk scores from a cox regression. For reasons not relevant to this topic, I must do it manually, as opposed to using the predict function in ...
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1answer
812 views
How can one invert hazard ratios and their confidence intervals?
Imagine that when we compare treatment A to treatment B there is an associated hazard ratio of 0.56 (95% CI: 0.36 to 0.87). Let's say that instead of this, I want the hazard ratio associated with ...
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1answer
178 views
use survfit with centered = FALSE, similar to basehaz
When using the basehaz() function (basehaz() calls on survfit()), there is an option to set <...
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13 views
the number of events
I am beginner in systematic review and currently I am undertaking a review and as a part of the extraction I would like to know how many events occurred in the treatment and control groups. In one ...
