Hazard Models

May 29 • Notes • 1516 Views • 3 Comments on Hazard Models

       Hazard Models:

There are many hazard models. Some of them are explained below.

1.    Proportional Hzard Models(PHM):

• It is a multivariate regression analysis.
• This is proposed by Cox in 1972.
•  The model has been developed for different applications in life tine analysis. This model estimates the effects of different covariates  like survival or reliability covariates influencing TTF of a system.
•  Mainly , all the models are based on proportional hazard models.
•  PHM is a very useful technique  as it helps in investigating explanatory variables in hazard of assets.
• It is available for both static and dynamic explanatory variables.
• This models handles truncated data, non truncated data and tied values.

 2.    Stratified Proportional Hzard Models(SPHM):

•  Based on the discrete values of single covariate or combination  of discrete values of a set of covariates, the population is divided into q levels in case of SPHM.
•  It is the useful extensions of PHM for its applications  in different situations.
•  This is distribution free.

3.    Additive Hazard Model:

•  when a system after repair is better than it was just before the repair, but not as  good as new this is additive model.
•  The hazard that is not zero at time zero is said by this model
•  It canot handle tied values.

4.    Mixed (Additive-Multiplicative) Model:

•  The hazard of an individual is considered as mixed model ,which contains both additive and multiplicative component.
•  Sometimes it gives much better fit to the data as compared to PHM.

5.    Accelerated Failure Time Model:

• The Accelerated Failure Time Model (AFTM) is the most common approaches which is used in obtaining reliability and failure rate estimates of devices and components in a much shorter time.

 6.    Extended Hzard Regression Model:

•  This is developed in 1985.
• This includes both PHM and AFTM.

Some questions and their answers.

Q1. Explain some of the five hazard models.

Ans.         Hazard Models:

There are many hazard models. Some of them are explained below.

1.    Proportional Hzard Models(PHM):

•  It is a multivariate regression analysis.
• This is proposed by Cox in 1972.
• The model has been developed for different applications in life tine analysis. This model estimates the effects of different covariates  like survival or reliability covariates influencing TTF of a system.
•  Mainly , all the models are based on proportional hazard models.
• PHM is a very useful technique  as it helps in investigating explanatory variables in hazard of assets.
•  It is available for both static and dynamic explanatory variables.
•  This models handles truncated data, non truncated data and tied values.

 2.    Stratified Proportional Hzard Models(SPHM):

• Based on the discrete values of single covariate or combination  of discrete values of a set of covariates, the population is divided into q levels in case of SPHM.
• It is the useful extensions of PHM for its applications  in different situations.
• This is distribution free.

3.    Additive Hazard Model:

• when a system after repair is better than it was just before the repair, but not as  good as new this is additive model.
•  The hazard that is not zero at time zero is said by this model
•  It canot handle tied values.

4.    Mixed (Additive-Multiplicative) Model:

• ØThe hazard of an individual is considered as mixed model ,which contains both additive and multiplicative component.
•  Sometimes it gives much better fit to the data as compared to PHM.

5.    Accelerated Failure Time Model:

•  The Accelerated Failure Time Model (AFTM) is the most common approaches which is used in obtaining reliability and failure rate estimates of devices and components in a much shorter time.

Accelerated Failure Time ModelAdditive Hazard ModelHazard ModelsMixed Additive-Multiplicative ModelProportional Hzard Models PHM

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