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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.
Internal consistency is usually measured with Cronbach's alpha, a statistic calculated from the pairwise correlations between items. Internal consistency ranges between negative infinity and one. Coefficient alpha will be negative whenever there is greater within-subject variability than between-subject variability. [1]
The absorption value for normal-incident light on graphene in vacuum would then be given by πα / (1 + πα/2) 2 or 2.24%, and the transmission by 1 / (1 + πα/2) 2 or 97.75% (experimentally observed to be between 97.6% and 97.8%). The reflection would then be given by π 2 α 2 / 4 (1 + πα/2) 2 .
This method provides a partial solution to many of the problems inherent in the test-retest reliability method. For example, since the two forms of the test are different, carryover effect is less of a problem. Reactivity effects are also partially controlled; although taking the first test may change responses to the second test.
For the reliability of a two-item test, the formula is more appropriate than Cronbach's alpha (used in this way, the Spearman-Brown formula is also called "standardized Cronbach's alpha", as it is the same as Cronbach's alpha computed using the average item intercorrelation and unit-item variance, rather than the average item covariance and ...
Cronbach can refer to: Abraham Cronbach (1882–1965), American Rabbi, teacher and known pacifist Lee Cronbach (1916–2001), American educational psychologist
It would be nice to have a guide as to what are considered adequate values for Cronbach alpha, what the implications are for using a test with a Cronbach alpha of, say .5 Tim bates 11:08, 9 October 2006 (UTC) Some people say that 0.70 is a professional standard for reliability. I'm not aware of where this comes from. I've also heard 0.60.
The source free equations can be written by the action of the exterior derivative on this 2-form. But for the equations with source terms (Gauss's law and the Ampère-Maxwell equation), the Hodge dual of this 2-form is needed. The Hodge star operator takes a p-form to a (n − p)-form, where n is the number of dimensions.