The parameters under this heading supply input data for the test plan.

Specifies the number of stresses used in the accelerated testing. Choices are 1 or 2. The default is 1. The selection you make here determines how may rows display in the table immediately below. In this table, you enter stress values.

The table in which to enter stress data. Depending on whether 1 or 2 is selected for Stress count, the table contains either one row or two rows. In each row, you select a life stress model and enter stress values. Because these values are calculation inputs, they cannot be blank. Only non-negative values can be entered. Descriptions of table columns follow.

The lifetime distribution of the component. When either Weibull or Lognormal is selected, a field for specifying the shape parameter is shown to the right. The value must be greater than 0. The default is 2.

The criteria by which to analyze the test plan. Choices vary based on whether 1 or 2 is selected for Stress count.

Choices for one stress are:

Choices for two stresses are:

The percent of units that should be tested at the middle stress level. This parameter is shown only when 3 Level Best Compromise Plan is selected for Test plan.

The value to use to adjust the 3 level 4:2:1 allocation plan. This parameter is shown only when 3 Level 4:2:1 Allocation Plan is selected for Test plan. The low stress level of this plan is multiplied by the value entered here. The product is then used as the low stress level for the test, and the middle stress level is readjusted to be as close as possible to halfway between the low and high stress levels. To get an unadjusted plan, you would enter a value of 1.

Indicates whether the number of units tested is available. When this checkbox is cleared (default), the number of units is not entered. When it is selected, a field becomes available to the right for entering the number of units. The value must be greater than or equal to 0. The default is 100.

The number of hours that the test runs. The value must be greater than or equal to 0. The default is 100.

Indicates the criteria to find the time of interest to which variance is minimized. Choices are Unreliability and Life Stress Parameters. The default is Unreliability. The selection you make here determines the prefix shown in the names for the stress parameters that appear below Usage level unreliability criterion.

A percentage value that indicates the unreliability of the system at the usage stress level.

As indicated earlier, your selection for Test parameter type determines the prefix shown for stress and their default values. Your selection for Stress count determines the number of required parameters. The unreliability for the highest stress cannot be less than the unreliability for the usage stress. The life stress parameter for the highest stress cannot be greater than the life stress parameter for the usage stress.

For a single stress, two parameters are required.

For two stresses, three parameters are required.

Prior to calculating the input data, the following message is shown in the table beneath this heading: There are no results to display. Once the input data is calculated, results for low and high stress levels are shown. One row exists for each stress level, with the number of levels noted in the selection for Test plan. For example, when 3 Level Best Compromise Plan is selected, the table has three rows. Column descriptions follow.

The first stress used in the accelerated test plan.

The second stress used in the accelerated test plan. This column is shown only when 2 is selected for Stress count to indicate that two stresses are applied.

The proportion of units tested at the stress level or, for two stresses, the stress level combination.

This column is shown only when Units on test is selected when the input data was calculated.

You use the Excel and Print buttons beneath the table to save results to a Microsoft Excel spreadsheet and print them to a printer. For more information, see Excel and Print Buttons.

Once the accelerated test plan is calculated, additional display-only results are shown beneath the table. The last two results, Total time and Standard deviation, are shown only when Units on test was selected when the input data was calculated.

The time at the unreliability corresponding to the usage stress.

The expected total test time of all components at all stress levels.

The standard deviation of the time at unreliability.