![]() The higher-order factor model requires the general factor and specific factor loadings to be equal, whereas the bi-factor model does not contain this constraint. Furthermore, Morgan, Hodge, Wells and Watkins provided some support for such a bias in a simulation study that found that, “when samples were generated from a true higher-order factor structure, approximate fit statistics tended to identify the bi-factor solution as best fitting.” More recently, Gignac has tried to explain the bias in terms of the proportionality constraint. The following are commonly used diagnostic labels together with corresponding numerical limits in terms of IQs and percentages.Recently, the bi-factor approach has been criticised for an inherent statistical bias that makes it more likely to have acceptable fit statistics than the higher-order factor model. More than 99 percent obtain scores between 55 and 145 (3 standard deviations from the mean). About 95 percent score between 70 and 130 (2 standard deviations on either side of the mean). About two-thirds of all adults obtain IQs between 85 and 115 (1 standard deviation below and above the mean). An IQ of 100 defines the performance of the average adult at that age. These five indexes were constructed to have means of 100 and standard deviations of 15 IQ points. Processing Speed Index (PSI) is the ability to process simple or routine visual material without making errors.Working Memory Index (WMI) is the ability to sustain attention, concentrate, and exert mental control.Perceptual Reasoning Index (PRI) is designed to measure fluid reasoning in the perceptual domain with tasks that assess nonverbal concept formation, visual perception and organization, visual-motor coordination, learning, and the ability to separate figure and ground in visual stimuli.Verbal Comprehension Index (VCI) is designed to measure verbal reasoning and concept formation.Full Scale IQ (FSIQ) is considered the most valid measure of overall cognitive ability.There are five aspects of intelligence that are identified: It is composed of 10 core subtests and five supplemental subtests. It can be administered to people between the ages of 16 and 90. The current version of the Wechsler Adult Intelligence Scale – (WAIS-IV) was released in 2008. The author of the original WAIS defined ‘intelligence’ as “ The global capacity of a person to act purposefully, to think rationally, and to deal effectively with his/her environment.” (David Wechsler, 1939. Wechsler Adult Intelligence Scale – IV (WAIS-IV) ![]()
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