Optimal Test Plan for Two Stresses - Revision history

Kate Racaza at 18:24, 28 September 2015

2015-09-28T18:24:20Z

← Older revision		Revision as of 18:24, 28 September 2015
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	{{Reference Example\|{{Banner ALTA Reference Examples}}}}		{{Reference Example\|{{Banner ALTA Reference Examples}}}}

	This example ~~compares~~ the results for the 3 level optimum test plan with two stresses.		This example validates the results for the 3 level optimum test plan with two stresses in ALTA.

Kate Racaza at 16:36, 13 June 2014

2014-06-13T16:36:05Z

← Older revision		Revision as of 16:36, 13 June 2014
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	{{Reference Example\|~~ALTA_Reference_Examples_Banner.png\|ALTA_Reference_Examples~~}}		{{Reference Example\|{{Banner ALTA Reference Examples}}}}

	This example compares the results for the 3 level optimum test plan with two stresses.		This example compares the results for the 3 level optimum test plan with two stresses.

Kate Racaza at 15:25, 13 June 2014

2014-06-13T15:25:08Z

← Older revision		Revision as of 15:25, 13 June 2014
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	{{Reference Example\|ALTA_Reference_Examples_Banner.png\|ALTA_Reference_Examples}}		{{Reference Example\|ALTA_Reference_Examples_Banner.png\|ALTA_Reference_Examples}}

	This example compares the results for the 3~~-Level Optimum~~ test plan with two stresses.		This example compares the results for the 3 level optimum test plan with two stresses.


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	{{Reference_Example_Heading2}}		{{Reference_Example_Heading2}}

	A Weibull distribution with the following life stress relationship is used.		A Weibull distribution with the following life-stress relationship is used.

	::<math>ln(\eta)=\beta_{0}+\beta_{1} \times log(vpm) + \beta_{2} \frac{11605}{temp}\,\!</math>		::<math>ln(\eta)=\beta_{0}+\beta_{1} \times log(vpm) + \beta_{2} \frac{11605}{temp}\,\!</math>
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	The resulting ~~three-level best compromise~~ test plan in ALTA is shown below.		The resulting test plan in ALTA is shown below.

	[[Image: Optimal plan test plan.png\|center\|700px]]		[[Image: Optimal plan test plan.png\|center\|700px]]

Kate Racaza at 16:45, 12 June 2014

2014-06-12T16:45:21Z

← Older revision		Revision as of 16:45, 12 June 2014
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	where ''temp'' is the temperature in K and ''vpm'' is the voltage stress in volts/mm. The planning values for the model parameters ~~used in~~ the test plan are:		where ''temp'' is the temperature in Kelvins and ''vpm'' is the voltage stress in volts/mm. The planning values for the model parameters for the test plan are:

	::<math>\beta = \frac{1}{\sigma} = 1.485\,\!</math>  ,   <math>\beta_{1} = 12.28\,\!</math>   and   <math>\beta_{2} = 0.3878\,\!</math>		::<math>\beta = \frac{1}{\sigma} = 1.485\,\!</math>  , <math>\beta_{0} = 58.173\,\!</math> ,  <math>\beta_{1} = -12.28\,\!</math>   and   <math>\beta_{2} = 0.3878\,\!</math>

	These planning values are given on page 535.		These planning values are given on page 535.
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	The use condition stress values are vpm = 80 volts/mm and temp = 120°C (393.15°K).		The use condition stress values are vpm = 80 volts/mm and temp = 120°C (393.15°K).

	The highest stress values that can be used in the test are vpm = 200 volts/mm and temp = 260°C (533.15°K).		The highest stress values that can be used in the test are: vpm = 200 volts/mm and temp = 260°C (533.15°K).

	A total of 170 units ~~are available for testing~~ for 1,000 hours. Three combinations of temperature and voltage levels can be used in the test. The ~~objective~~ of the test plan is to:		A total of 170 units will tested for 1,000 hours. Three combinations of temperature and voltage levels can be used in the test. The objectives of the test plan are to:

	* Determine the three stress combinations used in the test.		* Determine the three stress combinations that should be used in the test.
	* Determine the number of test units at each stress combination.		* Determine the number of test units at each stress combination.

	Tests will be conducted using the created test plan. The failure data from the test will be used to estimate the model parameters~~. The estimated parameters~~ are then used to predict the B10 life at vpm = 80 volts/mm and temp = 120°C.		Tests will be conducted using the created test plan. The failure data from the test will be used to estimate the model parameters, which are then used to predict the B10 life at vpm = 80 volts/mm and temp = 120°C. Therefore, we need a test plan that will minimize the estimation variance of the B10 life at the given usage stress level.

	~~We need to find a test plan that will minimize the estimation variance of the B10 life at the given usage stress level.~~

			{{Reference_Example_Heading3}}

			The three stress combinations and the number of test units at each of them are:
			:* 62 units should be tested at 124 volts and 260°C (533.15°K)
			:* 42 units should be tested at 159 volts and 120°C (393.15°K)
			:* 66 units should be tested at 200 volts and 260°C (533.15°K)

			Based on this test plan, the estimated standard error for the B10 life at vpm = 80 volts/mm and temp = 120°C is <math>Ase \left[log(\hat{t}_{0.1}(50))\right]\,\!</math> = 0.3670 .

			The standard error is calculated from the result in Table 20.6, as shown next:

	{{~~Reference_Example_Heading3~~}}		::<math>\frac{n}{\sigma^{2}}Var\left[log(\hat{t}_{0.1}(50)) \right] = 50.5\,\!</math>

	* The three stress combinations and the number of test units at each of them are:
	~~:* 62 units will be tested at voltage of 124 and temperature of 260°C (533.15°K)~~
	~~:* 42 units will be tested at voltage of 159 and temperature of 120°C (393.15°K)~~
	~~:* 66 units will be tested at voltage of 200 and temperature of 260°C (533.15°K)~~
	* The estimated standard error for the B10 life at vpm = 80 volts/mm and temp = 120°C from this test plan is <math>Ase \left[log(\hat{t}_{0.1}(50))\right]\,\!</math> = 0.3670 .

	~~The standard error is calculated from the result in Table 20.6. In Table 20.6, the value for <math>\frac{n}{\sigma^{2}}Var\left[log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 50.5.~~ Since n = 170 and <math>\frac{1}{\sigma^{2}} = \beta^{2}\,\!</math> = 2.205229, so   <math>Var\left [log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 0.1347. Therefore, <math>Ase \left[log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 0.3670.		Since n = 170 and <math>\frac{1}{\sigma^{2}} = \beta^{2}\,\!</math> = 2.205229, so   <math>Var\left [log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 0.1347. Therefore, <math>Ase \left[log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 0.3670.


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	The probabilities of failure (%) at time of 1000 are calculated based on test planning values. For example, at the use stress of voltage and at the maximum stress of temperature, the life characteristic is:		The probabilities of failure (%) at time 1000 are calculated based on the test planning values. For example, at the use stress of voltage and at the maximum stress of temperature, the life characteristic is:


	::<math>\begin{align}		::<math>\begin{align}
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	Therefore, <math>\eta\,\!</math> = 363269. The probability of failure is calculated by:		Therefore, <math>\eta\,\!</math> = 363269. The probability of failure is calculated by:


	::<math>\begin{align}		::<math>\begin{align}
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	The three level best compromise test plan in ALTA is shown below.		The resulting three-level best compromise test plan in ALTA is shown below.

	[[Image: Optimal plan test plan.png\|center\|700px]]		[[Image: Optimal plan test plan.png\|center\|700px]]


	The test plan shows that:		The test plan shows that (starting at row 29 in the picture above):

	* The first stress level ~~(row 29)~~ should be a combination of 200 volts and 260°C (533.15°K) and about 56 units should be tested at that level.		* The first stress level should be a combination of 200 volts and 260°C (533.15°K) and about 56 units should be tested at that level.
	* The second stress level ~~(row 30)~~ should be a combination of 129 volts and 260°C (533.15°K) and about 71 units should be tested at that level.		* The second stress level should be a combination of 129 volts and 260°C (533.15°K) and about 71 units should be tested at that level.
	* The third stress level (row 31) should be a combination of 165 volts and 120°C (393.15°K) and about 43 units should be tested at that level.		* The third stress level (row 31) should be a combination of 165 volts and 120°C (393.15°K) and about 43 units should be tested at that level.

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	The above results are different from the results given in the book. In the following discussion, a simulation study is conducted to check the results obtained from ALTA.		The above results are different from the results given in the book. In the following discussion, a simulation study is conducted to check the results obtained from ALTA.

	~~'''Using ALTA SimuMatic to Evaluate the Test Plan'''~~

	We will use the SimuMatic utility to evaluate the test plan. The following picture shows the settings used in the Main tab of SimuMatic (with <math>\alpha_{1} = \beta_{1} \times 11605\,\!</math>):		'''Using SimuMatic to Evaluate the Test Plan'''

			We will use the ALTA SimuMatic utility to evaluate the test plan. The following picture shows the settings used in the Main tab of SimuMatic (with <math>\alpha_{1} = \beta_{1} \times 11605\,\!</math>):

	[[Image: Optimal plan simumatic1.png\|center\|550px]]		[[Image: Optimal plan simumatic1.png\|center\|550px]]


	The rest of the SimuMatic ~~settings~~ are as follows:		The rest of the settings in SimuMatic are as follows:

	* Stress tab:		* Stress tab:
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	* Settings tab		* Settings tab
	::Seed = '''10''', Precision = '''4''', Number of data sets = '''1000'''		::Seed = '''10''', Precision = '''4''', Number of data sets = '''1000'''
	* Reliabilities and Times		* Reliabilities and Times tab
	::Reliability value = '''0.9'''		::Reliability value = '''0.9'''

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	We take the ~~nature~~ log of the B10 life (the last column) and calculate its standard deviation. The calculated standard deviation is 0.2629. This is very close to the analytical solution from the ALTA test plan tool, where the standard deviation is 0.2623.		We take the natural log of the B10 life (the last column) and calculate its standard deviation. The calculated standard deviation is 0.2629. This is very close to the analytical solution from the ALTA test plan tool, where the standard deviation is 0.2623.

	This standard deviation is smaller than the standard deviation given by the test plan in the book. Therefore, the test plan generated in ALTA is better than the test plan given in the book in terms of minimizing the estimation variance of the B10 life.		This standard deviation is smaller than the standard deviation given by the test plan in the book. Therefore, the test plan generated in ALTA is better than the test plan given in the book in terms of minimizing the estimation variance of the B10 life.

Kate Racaza at 17:57, 11 June 2014

2014-06-11T17:57:46Z

← Older revision		Revision as of 17:57, 11 June 2014
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	{{Reference Example\|ALTA_Reference_Examples_Banner.png\|ALTA_Reference_Examples}}		{{Reference Example\|ALTA_Reference_Examples_Banner.png\|ALTA_Reference_Examples}}

	This example compares the results ~~from~~ the ~~statistically optimum~~ test plan ~~in the ALTA test plan tool for~~ two stresses.		This example compares the results for the 3-Level Optimum test plan with two stresses.

Kate Racaza at 17:49, 11 June 2014

2014-06-11T17:49:58Z

← Older revision		Revision as of 17:49, 11 June 2014
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	'''Using ALTA SimuMatic to Evaluate the Test Plan'''		'''Using ALTA SimuMatic to Evaluate the Test Plan'''

	We will use the SimuMatic utility to evaluate the test plan. The following ~~pictures show~~ the settings used in SimuMatic (with <math>\alpha_{1} = \beta_{1} \times 11605\,\!</math>):		We will use the SimuMatic utility to evaluate the test plan. The following picture shows the settings used in the Main tab of SimuMatic (with <math>\alpha_{1} = \beta_{1} \times 11605\,\!</math>):

	[[Image: Optimal plan simumatic1.png\|center\|550px]]		[[Image: Optimal plan simumatic1.png\|center\|550px]]


	~~[[Image~~: ~~Optimal plan simumatic2.png\|center\|550px]]~~		The rest of the SimuMatic settings are as follows:

			* Stress tab:
	~~[[Image~~: ~~Optimal plan simumatic3~~.~~png\|center\|550px]]~~		::Use level = '''80''', Transformation = '''Logarithmic'''
			::Use level = '''393.15''', Transformation = '''Reciprocal'''
			* Censoring tab:
	~~[[Image~~: ~~Optimal plan simumatic4~~.~~png\|center\|550px]]~~		::Right censoring after time '''1000'''.
			* Settings tab
			::Seed = '''10''', Precision = '''4''', Number of data sets = '''1000'''
	~~[[Image~~: ~~Optimal plan simumatic5~~.~~png\|center\|550px]]~~		* Reliabilities and Times
			::Reliability value = '''0.9'''

Kate Racaza at 16:15, 11 June 2014

2014-06-11T16:15:55Z

← Older revision		Revision as of 16:15, 11 June 2014
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	{{Reference_Example_Heading4\|ALTA}}		{{Reference_Example_Heading4\|ALTA}}

	The planning information is entered in ALTA as shown below.		The planning information is entered in ALTA, as shown below.

			[[Image:Optimal plan 2 stresses.png\|center]]


			The probabilities of failure (%) at time of 1000 are calculated based on test planning values. For example, at the use stress of voltage and at the maximum stress of temperature, the life characteristic is:


			::<math>\begin{align}
			ln(\eta) =& \beta_{0}+\beta_{1} \times log(vpm) + \beta_{2} \frac{11605}{temp} \\
			=& 58.173 - 12.28 \times ln(80) + 0.3878 \frac{11605}{533.15}\\
			=& 12.8029
			\end{align}\,\!</math>


			Therefore, <math>\eta\,\!</math> = 363269. The probability of failure is calculated by:


			::<math>\begin{align}
			P(Time, Use Stress 1, Maximum Stress 2) =& P(1000, 80, 533.15)\\
			=& 1 - e^{-\left(\frac{1000}{363269} \right)^{1.485}}\\
			=& 0.000158 = 0.0158%
			\end{align}\,\!</math>


			The three level best compromise test plan in ALTA is shown below.

			[[Image: Optimal plan test plan.png\|center\|700px]]


			The test plan shows that:

			* The first stress level (row 29) should be a combination of 200 volts and 260°C (533.15°K) and about 56 units should be tested at that level.
			* The second stress level (row 30) should be a combination of 129 volts and 260°C (533.15°K) and about 71 units should be tested at that level.
			* The third stress level (row 31) should be a combination of 165 volts and 120°C (393.15°K) and about 43 units should be tested at that level.


			The estimated standard deviation of the log B10 life at 50°C can be obtained by:

			::<math>Ase \left[ log \left(\hat{t}_{0.1}(50) \right)\right] = \frac{Ase\left(\hat{t}_{0.1}(50) \right)}{\hat{t}_{0.1}(50)} = \frac{422947.9056}{1612671} = 0.262265\,\!</math>


			The above results are different from the results given in the book. In the following discussion, a simulation study is conducted to check the results obtained from ALTA.

			'''Using ALTA SimuMatic to Evaluate the Test Plan'''

			We will use the SimuMatic utility to evaluate the test plan. The following pictures show the settings used in SimuMatic (with <math>\alpha_{1} = \beta_{1} \times 11605\,\!</math>):

			[[Image: Optimal plan simumatic1.png\|center\|550px]]


			[[Image: Optimal plan simumatic2.png\|center\|550px]]


			[[Image: Optimal plan simumatic3.png\|center\|550px]]


			[[Image: Optimal plan simumatic4.png\|center\|550px]]


			[[Image: Optimal plan simumatic5.png\|center\|550px]]


			The simulation results are shown next.

			[[Image: Optimal plan simumatic6.png\|center\|700px]]


			We take the nature log of the B10 life (the last column) and calculate its standard deviation. The calculated standard deviation is 0.2629. This is very close to the analytical solution from the ALTA test plan tool, where the standard deviation is 0.2623.

			This standard deviation is smaller than the standard deviation given by the test plan in the book. Therefore, the test plan generated in ALTA is better than the test plan given in the book in terms of minimizing the estimation variance of the B10 life.

Kate Racaza at 23:14, 10 June 2014

2014-06-10T23:14:23Z

← Older revision		Revision as of 23:14, 10 June 2014
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	These planning values are given on page 535.		These planning values are given on page 535.

	The use condition stress values are ''vpm'' = 80 volts/mm and ''temp'' = 120°C (393.15°K).		The use condition stress values are vpm = 80 volts/mm and temp = 120°C (393.15°K).

	The highest stress values that can be used in the test are ''vpm'' = 200 volts/mm and ''temp'' = 260°C (533.15°K).		The highest stress values that can be used in the test are vpm = 200 volts/mm and temp = 260°C (533.15°K).

	A total of 170 units are available for testing for 1,000 hours. Three combinations of temperature and voltage levels can be used in the test. The objective of the test plan is to:		A total of 170 units are available for testing for 1,000 hours. Three combinations of temperature and voltage levels can be used in the test. The objective of the test plan is to:
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	* Determine the number of test units at each stress combination.		* Determine the number of test units at each stress combination.

	Tests will be conducted using the created test plan. The failure data from the test will be used to estimate the model parameters. The estimated parameters are then used to predict the B10 life at ''vpm'' = 80 volts/mm and ''temp'' = 120°C.		Tests will be conducted using the created test plan. The failure data from the test will be used to estimate the model parameters. The estimated parameters are then used to predict the B10 life at vpm = 80 volts/mm and temp = 120°C.

	We need to find a test plan that will minimize the estimation variance of the B10 life at the given usage stress level.		We need to find a test plan that will minimize the estimation variance of the B10 life at the given usage stress level.
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	{{Reference_Example_Heading3}}		{{Reference_Example_Heading3}}

			* The three stress combinations and the number of test units at each of them are:
			:* 62 units will be tested at voltage of 124 and temperature of 260°C (533.15°K)
			:* 42 units will be tested at voltage of 159 and temperature of 120°C (393.15°K)
			:* 66 units will be tested at voltage of 200 and temperature of 260°C (533.15°K)
			* The estimated standard error for the B10 life at vpm = 80 volts/mm and temp = 120°C from this test plan is <math>Ase \left[log(\hat{t}_{0.1}(50))\right]\,\!</math> = 0.3670 .

			The standard error is calculated from the result in Table 20.6. In Table 20.6, the value for <math>\frac{n}{\sigma^{2}}Var\left[log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 50.5. Since n = 170 and <math>\frac{1}{\sigma^{2}} = \beta^{2}\,\!</math> = 2.205229, so   <math>Var\left [log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 0.1347. Therefore, <math>Ase \left[log(\hat{t}_{0.1}(50)) \right]\,\!</math> = 0.3670.


	{{Reference_Example_Heading4\|ALTA}}		{{Reference_Example_Heading4\|ALTA}}

			The planning information is entered in ALTA as shown below.

Kate Racaza: Created page with '{{Reference Example|ALTA_Reference_Examples_Banner.png|ALTA_Reference_Examples}} This example compares the results from the statistically optimum test plan in the ALTA test plan…'

2014-06-10T22:38:52Z

Created page with '{{Reference Example|ALTA_Reference_Examples_Banner.png|ALTA_Reference_Examples}} This example compares the results from the statistically optimum test plan in the ALTA test plan…'

New page

{{Reference Example|ALTA_Reference_Examples_Banner.png|ALTA_Reference_Examples}}

This example compares the results from the statistically optimum test plan in the ALTA test plan tool for two stresses.

{{Reference_Example_Heading1}}

The data set is from Example 20.8 on page 549 in the book ''Statistical Methods for Reliability Data'' by Dr. Meeker and Dr. Escobar, John Wiley & Sons, 1998.

{{Reference_Example_Heading2}}

A Weibull distribution with the following life stress relationship is used.

::<math>ln(\eta)=\beta_{0}+\beta_{1} \times log(vpm) + \beta_{2} \frac{11605}{temp}\,\!</math>

where ''temp'' is the temperature in K and ''vpm'' is the voltage stress in volts/mm. The planning values for the model parameters used in the test plan are:

::<math>\beta = \frac{1}{\sigma} = 1.485\,\!</math>  ,   <math>\beta_{1} = 12.28\,\!</math>   and   <math>\beta_{2} = 0.3878\,\!</math>

These planning values are given on page 535.

The use condition stress values are ''vpm'' = 80 volts/mm and ''temp'' = 120°C (393.15°K).

The highest stress values that can be used in the test are ''vpm'' = 200 volts/mm and ''temp'' = 260°C (533.15°K).

A total of 170 units are available for testing for 1,000 hours. Three combinations of temperature and voltage levels can be used in the test. The objective of the test plan is to:

* Determine the three stress combinations used in the test.
* Determine the number of test units at each stress combination.

Tests will be conducted using the created test plan. The failure data from the test will be used to estimate the model parameters. The estimated parameters are then used to predict the B10 life at ''vpm'' = 80 volts/mm and ''temp'' = 120°C.

We need to find a test plan that will minimize the estimation variance of the B10 life at the given usage stress level.

{{Reference_Example_Heading3}}
{{Reference_Example_Heading4|ALTA}}