Questions tagged [accelerated-failure-time]
12 questions
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votes
1 answer
AFT models in Stata with time-varying covariates
The AFT models from Stata's streg can handle time-varying covaraites. In particular, the manual states that
streg is suitable only for data that have been stset. By stsetting your data, you define the
variables _t0, _t, and _d, which serve as the…
Benjamin Christoffersen
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2 answers
Scale Parameter in a Log-Linear Accelerated Failure Time Model
Let the logarithm of the random varible $T_i$, associated with the lifetime of the $i$th individual in a survival study, follow the disitribution
$$log(T_i) = \mu + X_i\beta + \sigma\epsilon_i$$
with $\mu$ being a constant that is equal for all…
Benkyozamurai
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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 $95\%$ prediction intervals in black. The green lines are the…
JLee
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Recurrent event data modelling - Cox PH or AFT?
I am attempting to model recurrent event data in Stata. My data is dataset of patient records and I am modelling a patients first delivery of a mobility aid and the subsequent deliveries of new mobility devices as their previous device will have…
owen1995
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1 answer
AFT model with varying production
I want to implement an AFT model to study the failure time of a product given it's width.
$$S(t|width)=S_0((\beta_0+\beta_1 \times width)t)$$
However the prodction has varied during the time (less production at the beginning of the commercialisation…
Bérénice
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1 answer
Assumptions of an Accelerated Failure Time model?
I have an AFT model, comparing the adjusted survival of 5 groups and seeming to give reasonable results. As I do not feel confident in survival modelling, does this model has assumptions that need to be tested before publishing its results?
If there…
st4co4
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flexsurvreg log logistic intercept in R
I'm trying to fit a log-logistic AFT model with flexsurvreg(). With AFT model,
$$\log T = \gamma_0 + \gamma_1 z_1 + \gamma_2 z_2 + \sigma W,$$ where W ~ standard logistic distribution.
Below is an example output from flexsurvreg
Estimates:
…
nens
0
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What is the distribution of response, if the error distribution is non-normal?
Consider the AFT model:
$Y=log(T)=\beta^T x + \epsilon=\mu + \epsilon$ ; where $\epsilon \sim Gumbel(\alpha, \beta)$.
What should be the distribution of $Y$?
Is it $Y \sim Gumbel(\mu+\alpha, \beta)$?
Dushi Fdz
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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 $S_0$ represent the survival function when there are no…
Dushi Fdz
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Implementing logistic regression model in prediction model - use outcome or probability?
My question deals with the principles or way of thinking about implementing a logistic regression model in a larger scale forward prediction.
Let's say I have a trained logistic model which can predict whether a machine component will fail or not.…
Fritz45
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Proof of the hazard of the AFT model
This is an attempt to prove the hazard function $h$ of the accelerated failure time model as presented by Klein and Moeschberger in "Survival Analysis: Techniques for Censored and Truncated Data," (2nd Edition, Springer, 2003) on page 47, Eqn…
user1916067
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D-Calibration for Survival Models with imbalanced outcomes
I am building an accelerated time failure (AFT) model on a highly imbalanced data set 90% survival 10% death. I understand that we can not use Brier score because of the outcome imbalance, Brier score dose not fair well with imbalanced data, and I…
user14473305
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