Lognormal MLE Solution with Right Censored Data: Difference between revisions

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{{Reference Example}}
{{Reference Example}}


This example compares the Lognormal MLE solution with Fisher matrix bound for right censored data.
This example validates the calculations for the Lognormal MLE solution with Fisher matrix bound for right censored data in Weibull++ standard folios.




{{Reference_Example_Heading1}}
{{Reference_Example_Heading1}}
The data on page 199 of the book ''Statistical Methods for Reliability Data'' by Dr. Meeker and Dr. Escobar, John Wiley & Sons, 1998 is used.
The data set on page 199 of the book ''Statistical Methods for Reliability Data'' by Dr. Meeker and Dr. Escobar, John Wiley & Sons, 1998 is used.




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* The MLE solution is <math>\hat{\mu} = 6.56, \ \hat{\sigma} = 0.543\,\!</math>.
* The MLE solution is <math>\hat{\mu} = 6.56, \ \hat{\sigma} = 0.543\,\!</math>.


* The variance and covariance matrix is  
* The variance and covariance matrix is  
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* The MLE solution and the variance/covariance matrix:
* The following picture shows the MLE solution and the variance/covariance matrix:


[[Image:Lg_right_censored_matrix.png|center]]
[[Image:Lg_right_censored_matrix.png|center]]




* The Fisher matrix bound for parameters:
* The Fisher matrix bound for parameters are:


:For Ln-mu (using normal approximation of Eqn. 8.7 on page 187):
:For Ln-mu (using normal approximation of Eqn. 8.7 on page 187):


::<math>[\hat{\mu}'_{L}, \hat{\mu}'_{U}] = \hat{\mu}' \pm z_{(1-\alpha \setminus 2)}se_{\hat{\mu}'}\,\!</math>
::<math>[\hat{\mu}'_{L}, \hat{\mu}'_{U}] = \hat{\mu}' \pm z_{(1-\alpha / 2)}se_{\hat{\mu}'}\,\!</math>




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::<math>\begin{alignat}{2}
::<math>\begin{alignat}{2}
[\hat{\mu}'_{L}, \hat{\mu}'_{U}] =& \hat{\mu}' \pm z_{(1-\alpha \setminus 2)}se_{\hat{\mu}'}\\
[\hat{\mu}'_{L}, \hat{\mu}'_{U}] =& \hat{\mu}' \pm z_{(1-\alpha /2)}se_{\hat{\mu}'}\\
=& 6.564256 \pm 1.96 \times (0.0581)^{0.5}\\
=& 6.564256 \pm 1.96 \times (0.0581)^{0.5}\\
=& [6.0918, 7.0366933]\\
=& [6.0918, 7.0366933]\\
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:For Ln-Std (using log-normal approximation of Eqn. 8.8 on page 188):
:For Ln-Std (using log-normal approximation of Eqn. 8.8 on page 188):


::<math>[\hat{\sigma}'_{L}, \hat{\sigma}'_{U}] = \hat{\sigma}'exp (\pm \frac{z_{(1-\alpha \setminus 2)}se_{\hat{\sigma'}}}{\hat{\sigma}'})\,\!</math>
::<math>[\hat{\sigma}'_{L}, \hat{\sigma}'_{U}] = \hat{\sigma}'exp (\pm \frac{z_{(1-\alpha /2)}se_{\hat{\sigma}'}}{\hat{\sigma}'})\,\!</math>




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::<math>\begin{alignat}{2}
::<math>\begin{alignat}{2}
[\hat{\sigma}'_{L}, \hat{\sigma}'_{U}] =& \hat{\sigma}'exp (\pm \frac{z_{(1-\alpha \setminus 2)}se_{\hat{\sigma'}}}{\hat{\sigma}'})\\
[\hat{\sigma}'_{L}, \hat{\sigma}'_{U}] =& \hat{\sigma}'exp (\pm \frac{z_{(1-\alpha /2)}se_{\hat{\sigma}'}}{\hat{\sigma}'})\\
=& 0.534049 \times exp(\pm \tfrac{1.96\times 0.040562^{0.5}}{0.534049})\\
=& 0.534049 \times exp(\pm \tfrac{1.96\times 0.040562^{0.5}}{0.534049})\\
=& [0.255, 1.118]\\
=& [0.255, 1.118]\\
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:The results in Weibull++ are:
:The following picture shows the results in Weibull++:


[[Image:Lg_right_censored_bounds.png|center]]
[[Image:Lg_right_censored_bounds.png|center]]

Latest revision as of 16:18, 28 September 2015

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Lognormal MLE Solution with Right Censored Data

This example validates the calculations for the Lognormal MLE solution with Fisher matrix bound for right censored data in Weibull++ standard folios.


Reference Case

The data set on page 199 of the book Statistical Methods for Reliability Data by Dr. Meeker and Dr. Escobar, John Wiley & Sons, 1998 is used.


Data

Number in State State F or S Time to Failure
1 F 252
1 F 315
1 F 369
1 F 403
1 F 474
15 S 500


Result

  • The MLE solution is [math]\displaystyle{ \hat{\mu} = 6.56, \ \hat{\sigma} = 0.543\,\! }[/math].
  • The variance and covariance matrix is
[math]\displaystyle{ \sum =\begin{bmatrix} 0.0581 & 0.0374 \\ 0.0374 & 0.0405 \end{bmatrix}\,\! }[/math]


Results in Weibull++


  • The following picture shows the MLE solution and the variance/covariance matrix:
Lg right censored matrix.png


  • The Fisher matrix bound for parameters are:
For Ln-mu (using normal approximation of Eqn. 8.7 on page 187):
[math]\displaystyle{ [\hat{\mu}'_{L}, \hat{\mu}'_{U}] = \hat{\mu}' \pm z_{(1-\alpha / 2)}se_{\hat{\mu}'}\,\! }[/math]


For a confidence level of 0.95, it is:
[math]\displaystyle{ \begin{alignat}{2} [\hat{\mu}'_{L}, \hat{\mu}'_{U}] =& \hat{\mu}' \pm z_{(1-\alpha /2)}se_{\hat{\mu}'}\\ =& 6.564256 \pm 1.96 \times (0.0581)^{0.5}\\ =& [6.0918, 7.0366933]\\ \end{alignat}\,\! }[/math]


For Ln-Std (using log-normal approximation of Eqn. 8.8 on page 188):
[math]\displaystyle{ [\hat{\sigma}'_{L}, \hat{\sigma}'_{U}] = \hat{\sigma}'exp (\pm \frac{z_{(1-\alpha /2)}se_{\hat{\sigma}'}}{\hat{\sigma}'})\,\! }[/math]


For confidence level of 0.95, it is:
[math]\displaystyle{ \begin{alignat}{2} [\hat{\sigma}'_{L}, \hat{\sigma}'_{U}] =& \hat{\sigma}'exp (\pm \frac{z_{(1-\alpha /2)}se_{\hat{\sigma}'}}{\hat{\sigma}'})\\ =& 0.534049 \times exp(\pm \tfrac{1.96\times 0.040562^{0.5}}{0.534049})\\ =& [0.255, 1.118]\\ \end{alignat} \,\! }[/math]


The following picture shows the results in Weibull++:
Lg right censored bounds.png