Questions tagged [identifiability]
A model is identifiable if a single set of parameters can be found that will yield the best fit.
264 questions
6
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2
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What does skewed distribution as posterior mean?
I am trying to estimate the values of three unknown parameters in the Ordinary Differential Equation (ODE) using pyMC. Physically, A should be smaller than both B and C. But, given the data and ODE I ...
7
votes
3
answers
366
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Asymptotics in case of non-identifiability
I am dealing with a situation, where my distribution, becomes non-identifiable with respect to the parameters. Can anyone suggest some reliable sources or references wherein I can find the asymptotic ...
5
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1
answer
175
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Why does glmer give a "nearly unidentifiable, rescale variables" message and glmmTMB does not, when fitting a binomial model?
I was fitting the following binary glmm with glmer:
...
0
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0
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82
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Identification of hierarchical model
Let $(Y_j,X_j)_{j=1}^n$ be i.i.d. observations. Consider the hierarchical model
\begin{align}
Y_j \mid \theta_j &\sim P(\theta_j), \label{eq:obs}\\
E(Y_j) &=\theta_j = g(Z_j), \label{...
0
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0
answers
61
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Identifiability of time series models
I want to make a model which predicts y based on previous y and x over time. There are 3 choices in my mind:
Model 1:
$y_t = \beta_0 + \beta_1 y_{t-1} + \gamma x_{t-1} + \epsilon_t$
where $\epsilon_t ...
0
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0
answers
109
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How to use profile likelihood to determine identifiability?
This is a follow up from my previous question Why is the profile likelihood used to determine if a model has a unique solution? . I am interested in knowing how Profile Likelihood can be used to ...
1
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0
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96
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Identification of mixture latent model [closed]
This is an identification problem of a mixture model:
So I have observed data $\{Y_1,...Y_J,X\}$, but full data is $\{Y_1,...Y_J, Z, X\}$, where $\{Y_1,...Y_J\}$ are iid draws from $f_{Y|Z}(y,z)$. $f_{...
3
votes
2
answers
114
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Identification in Causal graph
I'm studying Brady Neal's book. I am doing the exercise on page 60, chapter 6, active reading exercise. ($T$ = treatment, $Y$ = target).
I am trying to figure out in the above graphs assuming the ...
0
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0
answers
41
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Wide intervals and oddly-shaped posterior densities of mixture‐model weights and means in Stan—should I be concerned?
I’m fitting a mixture model in Stan to strictly positive data. Each component distribution has a mean that can be expressed by some summation of a and b. (a and b are two “factor” parameters shared ...
7
votes
1
answer
311
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Identifiability with negative binomial model
Consider the following model:
$X_i \mid N \sim \text{Binomial}(N, \theta)$ and
$N \sim \text{Neg-Bin}(\mu, \varphi)$ (parametrized by mean and dispersion). Is this model identifiable? How to prove it?
...
6
votes
2
answers
875
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How to tell if a model is identifiable?
I am trying to find some references which explain how do we know that a statistical model is identifiable. My current understanding of identifiability is when only a single set of solutions exist for ...
1
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1
answer
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Structural Vector Autoregression: proof of the $(𝐾^2−𝐾)/2$ restrictions and identifiability?
I'm currently using Structural vector autoregressive models by Kevin Kotzé to learn Vector Autoregression. One of the points that it makes is the following:
the number of restrictions that we need to ...
4
votes
1
answer
330
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A model suffering from omitted variable bias can be said to be unidentified?
If my regression model
$$
y_i = \alpha + \beta x_i + \epsilon_i
$$
suffers from OVB the error contains one variable which we assume correlated with
$$
\epsilon_i = \gamma w_i + u_i
$$
my estimate of $\...
1
vote
1
answer
107
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Connection between multicollinearity and problem of identification in Simultaneous Equations Model
Is there any connection between multicollinearity and problem of identification in Simultaneous Equations Model?
I know multicollinearity is the occurrence of high intercorrelations among two or more ...
3
votes
1
answer
96
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Understanding how to evaluate the integral causal-effect expression
I have this expression
$$\begin{multline}
p( Y \mid \text{do}(Z=z)) = \\
\int_{B, S, W, X} dBdSdWdX \ \ P(B | S) P(W | B, S) P(X | B, S, Z=z) \\ \left[ \int_{Z'} dZ' P(Z'| B,S,W) P(Y | B, S, W, X, Z'...