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Option
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Description
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Solve for
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The value for which to solve. Choices are Test time or Test units.
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Parameters
The parameters under this heading specify the values needed to solve the problem.
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Demonstration type
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The demonstration type. Choices are Reliability, MTBF, Characteristic Life, and LX. This last type is the age at which X percent of the population is expected to fail. The selection for this parameter determines the parameters that appear immediately beneath it.
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Reliability, MTBF, Characteristic life, or X-value (%)
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The known value to use to compute test time or test units given the demonstration type. The defaults depend on the demonstration type. For example, for Reliability, the default is 0.9. For X-value (%), the default is 10.
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Confidence level (%)
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The percentage value to use to calculate the confidence bounds. The default is 90.
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Allowable failures
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The number of allowable failures. The default is 1.
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Time OR LX
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If Reliability is the demonstration type, Time is shown so that you can enter the amount of time it takes to test each item. The default is 100. If MTBF is the demonstration type, no parameter is shown in this same area. If LX is the demonstration type, LX is shown so that you can enter the age at which X percent of the population is expected to fail. The value for the X-Value (%) parameter specifies the percentage of the population expected to fail. The default is 100. Examples of entering LX values follow:
• L[X] = The age at which X percent of the population is expected to fail.
• L1 = The age at which 1 percent of the population is expected to fail.
• L10 = The age at which 10 percent of the population is expected to fail.
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Test units OR Test time
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When Test time is the value for which you are solving, Test units parameter is so that you can enter the number of units tested. When Test units is the value for which you are solving, Test time is shown so that you can enter the time spent testing.
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Distribution
The parameter under this heading specify the distribution and required values.
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Distribution type
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The distribution type. Choices are Weibull, Lognormal, Normal, Gumbel- (Lower), Gumbel+ (Upper), Exponential, and Rayleigh. The default is Weibull. The selection you make here determines whether a slope parameter is entered. If so, the field for entering slope is shown. For more information, see Failure and Repair Distributions.
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(Slope)
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The slope parameter for the distribution. If Exponential or Rayleigh is the distribution selected, this parameter is not shown.
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Plot and table options
The options under this heading specify the number of units and number of failures to use when generating the plot and result table. For more information, see Result Plot and Result Table.
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Test time OR Number of units
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When Test time is the value for which you are solving, the range for the number of units tested is specified by From, To, and Increment. When Test units is the value for which you are solving, the range for the test times is specified by From, To, and Increment.
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Number of failures
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The range for the number of failure occurrences to plot is specified in the From, To, and Increment options.
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Result
Once you click Calculate, this display-only field displays the calculated result for the value for which to solve.
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Test time OR Test units
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The calculated result for the value for which you solved.
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