Questions tagged [weibull-distribution]
The Weibull distribution is a probability distribution with applications in survival analysis, reliability engineering, failure analysis, industrial engineering, extreme value theory, weather forecasting, forestry, and more.
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Interpreting shape and rate parameters from a weibull model of mortality hazard in BaSTA
I am using the BaSTA package in R to estimate sex differences in survival parameters for a capture-recapture dataset. When I use a simple Gompertz model the parameters are very interpretable (b0 ...
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Obtain the survival function plot by building an overall survival regression model
I need to build an overall survival regression model that can show the survival plots for id's with multiple rows.
I have used the Weibull function to define the baseline hazard function h0(t) and Cox ...
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Maximum likelihood fit of left truncated Weibull distribution
I want to fit some samples to the right tail of a Weibull distribution. To fix the notation:
the samples are $\{X_i\}_{i=1,\ldots,n}$,
all samples are greater than a fixed threshold $L$,
the $X_i$'...
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Calculate survival function for remaining life prediction using CoxTimeVaryingFitter in Python
Cox’s time-varying hazard model is given here which is "CoxTimeVaryingFitter"
The mathematical formulation is represented as:
The values of log partial hazards "(x−x¯)′β" are ...
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Calcuate the coefficients of time varying covariates in Cox hazard model
The cox time varying covariates (x(t)) model is as such:
The above formulation can be seen here: https://lifelines.readthedocs.io/en/latest/fitters/regression/CoxTimeVaryingFitter.html
Here, can ...
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Showing suspended (right-censored) data points in diagram (distributed on x-axis)
How is it possible to show the suspended (right-censored) datapoints (distributed on x-axis without value for y-axis) in e.g. Probability Plot - Weibull CDF like the green triangles in attached image?
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Mean Residual Life of Weibull Distribution closed form
Weibull distribution function is parameterized as $ F(x) = 1 - e^{(-(x/\sigma)^a)}$ and survival function is $S(x)= e^{(-(x/\sigma)^a)}$ where $a$ is shape parameter and $\sigma$ is the scale ...
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Weibull distribution parameterization
I have the following Weibull distribution:
$f(x;\lambda,\beta) = (\lambda\beta)x^{(\beta-1)}e^{(-\lambda x^b)} $ where $\lambda$ is scale parameter and $\beta$ is shape parameter.
I have an ...
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Why does manually computed weibull hazard not match formula?
I'm trying to understand survival analysis better and ran into a weird problem with hazard rates - when I calculate it by hand,
i.e. with
$$
h(t) = \left( \frac{ P(T \leq t + \Delta t) - P(T \leq t)}{...
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How to estimate the variance covariance matrix of a Weibull survival model manually?
In flexsurv the var-covar matrix of the parameters can be produced with the vcov() function. This will produce a var-ovar matrix for the shape and scale parameters provided by the function coef(). ...
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How to prove the MLE for Weibull distribution is biased or unbiased?
My attempt is like this:
Let $X \sim \text{Weibull}(\alpha, \lambda)$ be a random variable following a Weibull distribution with pdf
$fx(x; \lambda) = \begin{cases}
{\alpha}{\lambda^{-\alpha}} x^{\...
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Extended Weibull-Cox model survival function
I'm reading an article where the authors use an extended Cox-Weibull hazard model with time-varying covariates to model survival time of an individual. This individual is allowed to start at week $m$, ...
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What is the motivation behind the inverse Weibull distribution
It seems like both the Weibull and the inverse or reversed Weibull model failure rates, waiting times and extreme phenomena.
The inverse Weibull pdf is
$$f_X(x; \alpha, \beta) = \beta \alpha^{-\beta}x^...
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How to calculate confidence intervall and z-score for a weibull distribution? (2 and 3 parameter)
How can i calculate the confidence interval (CI) of a weibull distribution?
I have raw data e.g.: 3,5,7,2,11,97, 223, ...
I can calculate the mean (µ), standard deviation (SD).
But how can i ...
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UMP Test and UMVUE when there are nuisance parameters
Consider $X_1,...,X_n \sim Weibull(\theta, c)$ where $c>0$ is unknown. Several textbook examples consider when $c$ is known, but here, we consider when $c$ is unknown. Suppose now we wanted to find ...
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Distribution is Weibull but variable diagnostics lines cross and converge - what to do?
Reproducible data:
...
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Finding shape and scale parameters of gamma distribution
I have a dataset [click here][1] and trying to find the shape and scale parameters of gamma distribution.
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Find extreme values in relative frequencies
I have the relative frequencies of elements in roughly 450 samples (with varying sample sizes). These elements are organisms in fecal samples.
I am interested in finding extreme values of these ...
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Is there an analytical equation for the uncertainty in an estimate of Weibull Modulus?
If I have a sample of $N$ measurements that follow a two-parameter Weibull distribution, how does the uncertainty in the estimate of the shape parameter (Weibull modulus, $k$) vary with $N$?
I've done ...
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What are the operational links between exponential and weibull distribution
I recently read a very interesting article about competing risks that came with simulations.
In these, the author defines a Weibull distributed variable w using an ...
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What is the meaning of the flexsurvreg plot and its res.t?
I use the flexsurverg to estimate the a Weibull survival model with a time varied covariate, where “utility” is a continuous function, and the result is shown as follows:
I plot the fit function and ...
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AFT model interpretation
I am slightly confused about the way accelerated failure time models work in comparison to proportional hazard models.
Is it a correct statement that while the PH model assumes covariates multiply ...
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Universal Approximation Capabilities of Mixture of Weibulls
Can a mixture of $N$ Weibull distributions approximate any continuous density with non-negative support, if $N$ is sufficiently large? (If so, a reference to the proof would be greatly appreciated).
(...
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Finding Variance of Proportional Hazards Regression Coefficient Estimates in Weibull Regression
So I am doing Weibull regression in R with the exponential relative risk function. The proportional hazards model formulation assumes that the hazard rate is given by $$\alpha(t;a,\sigma, \boldsymbol ...
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Predicting failure (e.g. from weibull) of part that has already survived a certain time
Simple question, but I'm overthinking it.
Say that I already have a cumulative failure distribution, cdf, (Weibull, but let's just assume any type of distribution) calculated from historical part data....
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How to calculate Weibull confidence interval using chi_square distribution/
I have a dataset, which I assume has a weibull distribution :
...
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Lifetime estimation - Weibull vs Survival
Survival analysis is mainly about estimating the lifetime of nearly anything or even anything:
And Weibull analysis is also about estimating the lifetime:
How are they different (in general) and ...
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Weibull Proportional Hazard in pymc
I’m looking to create a Bayesian proportional hazard model where the baseline hazard is modeled by a Weibull distribution (or some similar continuous distribution).
I’ve reviewed (and implemented) the ...
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Identify / separate sorts of failure
I ran a Weibull analysis on data of devices which consists mainly of failures over time (80 % died, 20 % are still alive). In total there are around ~4500 devices.
After conducting this analysis I ...
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Is a radioactive process describable by survival analysis?
According to this source, the survival function is defined as
$ S(t) = e^{- \lambda \cdot t} $
while, according to this source, the number at time $ t $ of radioactive atoms is
$ N(t) = N_0 \cdot e^{- ...
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Schoenfeld residuals - theoretical question
I have a doubt about the Schoenfeld residuals that are used to check the Cox proportional hazard model.
The residuals formula is:
$$\hat{r}_{ik}=c_i(x_{ik}-\hat{\bar{x}}_{w_ik})$$
$$\hat{\bar{x}}_{...
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Component reliability with an uncertain starting time
I have a lab data analysis challenge which I think can be viewed as a kind of reliability analysis problem.
Imagine a warehouse is filled with light bulbs that were installed at some unknown times in ...
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Are there any Python packages which can fit Conditional Weibull Distributions
I'm trying to fit failure data which already has a burn in time, and Im in need to use the Conditional Weibull Distribution. Are there any Python packages which have this distribution implemented?
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Why do our devices fail?
I would like to figure out why some devices of my company fail. Therefore, I'm able to use a list in which around 300 devices are listed together with about 70 parameters while only half of it is ...
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Predicting time to event / duration data
I've built a parametric survival model (survreg in R) to predict injury recovery duration using features such as age and treatments. I'm looking at trying model-based boosting using mboost with ...
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How to find shape and scale parameters for a Weibull distribution in survival analysis
I am to run a superiority clinical trial and I want to fit a parametric model under the Weibull Distribution.
But I am confused about how should I find the shape and scale parameters for the Weibull ...
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Weibull and Lognormal Fits
I have simulated failure time data for some components.
I tested whether a Weibull or lognormal distribution best fit the data. Please see Figures below. The figures provide median and $95\%$ ...
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Estimating Right Censored Data
I'm a newbie at Math, and I am just getting my feet wet when it comes to understanding math and statistics so please forgive my ignorance or question if it's already been answered or if materials are ...
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Decay function (e.g. weibull?) with numeric (i.e. not survival analysis) data
An example data frame:
...
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Weibull plot to assess goodness of fit
I would like show whether my data fit a Weibull distribution.
What kinds of graph should I plot?
Is the following graph appropriate one and what is this called?
How can I plot it in R?
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Interpretation of Weibull Survival Time Prediction from a Survreg Object
Code is somewhat like this:
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Finding the inputs and outputs of a Weibull distribution
If I have a Weibull distribution with a CDF of: $P_\theta (\lambda ,k) = (\frac{k}{\lambda })(\frac{x_i}{\lambda})e^{-(\frac{x_i}{\lambda})^k}$ for $x_i > 0$
And a MSE of:
$J_{\lambda ,k}(x) = \...
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Can we force a fitted distribution to have the same mean as the data?
I have some rainfall data that I am fitting with a Weibull distribution. The mean of the rainfall data is 0.62, but the mean of the best-fit Weibull distribution is 0.69. As a result, when I simulate ...
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Finding a distribution of Accelerated Failure Model
Can someone please answer these 3 questions related to AFT model?
In Accelerated Failure Time (AFT) model, $S(t│β,x)=S_0 (exp(β^T x).t)$, where $S_0$ is the baseline survival function, does $S_0$ ...
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Conjugate Prior for Alpha Power Inverse Weibull Distribution
Let $X$ has Alpha Power Inverse Weibull (APIW) distribution with pdf
$f(x) = \frac{\log \alpha}{\alpha - 1} \lambda \beta x^{-(\beta+1)} e^{-\lambda x^{-\beta}} \alpha^{e^{-\lambda x^{-\beta}}}, \; x&...
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Test whether two separate Weibull distributions describe the data better than a single Weibull distribution
My question is very similar to this one, but with the Weibull distribution replacing the Poisson distribution.
Let's say I am analyzing the distribution of times between failures for an engine, with ...
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Understanding the probability distributions behind a Monte Carlo experiment
A colleague and I are trying to model the expected maintenance cost/h (E[C/h]) of a component A on an aircraft over its life based on its reliability distribution. As the component fail, it's replaced ...
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Predicting survival/event probability with multi-level Weibull model and time-dependent covariates
I am still a beginner when it comes to survival analysis. I have fitted a parametric (Weibull) survival regression model with time-dependent covariates using the R package flexsurv via:
...
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Uniformly Most Powerful Test for Weibull Distribution
$\newcommand{\szdp}[1]{\!\left(#1\right)} \newcommand{\szdb}[1]{\!\left[#1\right]}$
Problem Statement: Let $Y_1,\dots,Y_n$ be a random sample from the probability
density function given by
$$f(y|\...
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