Design of Experiments Guide  • Accelerated Life Test Designs • Accelerated Life Test Plan Window • Review Balanced Design Diagnostics and Update Specifications
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Review Balanced Design Diagnostics and Update Specifications
Three new outlines are added to the window. Two of these give results for a balanced design, enabling you to compare results for a balanced design to those for an optimal design:
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Candidate Runs
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Parameter Variance for Balanced Design
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Distribution Profiler
Additional Outline Nodes
Candidate Runs
Enter the minimum and maximum number of units allowed at each setting of the acceleration factors. If you are augmenting a previous experiment, for each setting, include the number of units already run at that setting in the Minimum Units.
Parameter Variance for Balanced Design
Gives a matrix proportional to the covariance matrix for the estimates of the acceleration model parameters for the balanced design.
Denote the matrix of first partial derivatives of the model with respect to the parameters, θ, by X. Denote the error variance by σ2. Under general conditions, the least squares estimator of θ is asymptotically unbiased with asymptotic covariance matrix given as follows:
The Parameter Variance for Balanced Design outline gives (X‘X)-1, where derivatives are calculated numerically. The calculation assumes that the values specified as Prior Mean are the true parameter values.
For more information, see Nonlinear Models in Nonlinear Designs.
Distribution Profiler
Provides a way to explore failure probabilities, based on the balanced design, as you vary the acceleration factors and time. The probabilities are based on the assumption that the values specified as Prior Mean are the true parameter values.
Click Update Profiler to update the profiler if changes are made to Distribution Choice, Prior Mean, or Design Choices.

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Help created on 9/19/2017