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Administering one form of the test to a group of individuals. At some later time, administering an alternate form of the same test to the same group of people. Correlating scores on form A with scores on form B. The correlation between scores on the two alternate forms is used to estimate the reliability of the test.
Failure rate. Failure rate is the frequency with which an engineered system or component fails, expressed in failures per unit of time. It is usually denoted by the Greek letter λ (lambda) and is often used in reliability engineering. The failure rate of a system usually depends on time, with the rate varying over the life cycle of the system.
Cronbach's alpha (Cronbach's ), also known as tau-equivalent reliability ( ) or coefficient alpha (coefficient ), is a reliability coefficient and a measure of the internal consistency of tests and measures. [1][2][3] It was named after the American psychologist Lee Cronbach. Numerous studies warn against using Cronbach's alpha unconditionally.
The Mil-HDBK-217 reliability calculator manual in combination with RelCalc software (or other comparable tool) enables MTBF reliability rates to be predicted based on design. A concept which is closely related to MTBF, and is important in the computations involving MTBF, is the mean down time (MDT). MDT can be defined as mean time which the ...
Annualized failure rate. Annualized failure rate (AFR) gives the estimated probability that a device or component will fail during a full year of use. It is a relation between the mean time between failure (MTBF) and the hours that a number of devices are run per year. AFR is estimated from a sample of like components—AFR and MTBF as given by ...
Software reliability is the probability that software will work properly in a specified environment and for a given amount of time. Using the following formula, the probability of failure is calculated by testing a sample of all available input states. Mean Time Between Failure (MTBF)=Mean Time To Failure (MTTF)+ Mean Time To Repair (MTTR ...
The Spearman–Brown prediction formula, also known as the Spearman–Brown prophecy formula, is a formula relating psychometric reliability to test length and used by psychometricians to predict the reliability of a test after changing the test length. [1] The method was published independently by Spearman (1910) and Brown (1910). [2][3]
The survival function is a function that gives the probability that a patient, device, or other object of interest will survive past a certain time. [1] The survival function is also known as the survivor function[2] or reliability function. [3] The term reliability function is common in engineering while the term survival function is used in a ...