Stat > Reliability/Survival > Test Plans > Accelerated Life Testing > Stresses
You must enter the design stress and test stress levels. By default, Minitab determines an optimal allocation of units across stress levels. Alternatively, you can provide your own allocations.
Design stress
Enter the stress level for normal-use conditions. For example, if you were testing a drill press for motor breakdown and the drill was commonly run at 4 RPM, enter 4.
Test stresses
Enter one or more stress levels to use for the test. You can type the stress levels, enter stored constants, or enter columns. Type or enter stored constants if the test stress levels are for a single test plan. Use columns for a set of test stress levels to evaluate a series of test plans. Each column represents the test stresses for one test plan.
The stress level is the amount of stress imposed on each unit for the test. When the expected life is too long to test practically, you can use stress levels that are higher than normal-use conditions to cause early failures. For more information, go to Stress levels for accelerated life test plans
User Defined Allocations for each Stress Level
Percent Allocations
Enter the percent of units to test at each test stress level. You can type the percent allocations, or enter columns or stored constants. Type or enter stored constants if the percent allocations are for a single test plan and sum to 100%. Use columns for a set of allocations for a series of test plans. The columns that you enter must be the same length as the columns of test stresses and must sum to 100%.
Search for the Best Allocation for each Stress Level
Select to have Minitab determine the optimal allocation for each stress level. The optimal allocation yields the smallest asymptotic variance of the parameter to be estimated. For more information on the methods used to allocate units for each stress level, go to Stress levels for accelerated life test plans and click "Allocation of test units across stress levels".
Step length in search
Enter a value between 0.01 and 0.5 to define the steps that Minitab uses to search through the range of each test stress. The default is 0.05. For more information, go to Stress levels for accelerated life test plans and click "Default ranges for proportionate allocation".
Number of "best" plans to output
Enter the number of test plans for Minitab to display. The default is 3.
