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Publication date: 11/10/2021

Reliability Demonstration Calculator Fields

Specify the following quantities and test settings:


The probability of a type I error, which is the probability of rejecting the null hypothesis when it is true. It is commonly referred to as the significance level of the test. The default alpha level is 0.05.


The assumed failure time distribution. Distributions available are: Weibull, Lognormal, Frechet, Loglogistic, SEV, Normal, LEV, and logistic. For more information about these distributions, see Statistical Details for the Life Distribution Platform in Reliability and Survival Methods.


The scale parameter for the failure time distribution.

Note: The Scale field is denoted Weibull β when the specified Distribution is Weibull.

Max Failures Tolerated

The maximum number of failures allowed for a successful test demonstration.

Reliability Standard

The definition of the standard that you are testing. This standard is based on a length of time and the probability of an items survival to that time.


The minimum length of time that an item under test should survive.

Probability of Surviving

The probability that the item under test survives until the defined Time of the reliability standard

Enter one of the following two values to calculate the other:

Time of Demonstration

The length of the demonstration in time.

Number of Units Tested

The number of units needed for the demonstration.

Calculator Buttons


Evaluates the missing value.


Returns to the previous Sample Size and Power launch window.

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