Two different IQ scales: Terman's Stanford-Binet and the Wechsler Adult Intelligence Scale-Third edition. The Standford-Binet is the best intelligence scale for predicting future academic achievement. The Wechsler scales are a group of intelligence tests which are more accurate at distinguishing between different types of intelligence.
Wechsler Adult Intelligence Scale subscores and subtests... Neurocognitive testing
TIL words Idiot Moron and Imbecile were medical terms to classify 'The Scale of Retardation' that was invented by psychologists to differentiate people with low IQ. This classification remained in use till 1970s. Each category had grades low grade imbecile 3rd grade moron etc.
▶ IQ, the Gifted and the Highly Gifted.wmv - YouTube Apart from the not telling which IQ scale they are using (it looks like SB Form L-M), this is an excellent explanation of the statistics. NB. It also misses the second mini-distribution within the gifted range which skews the statistics slightly - ( there are more kids in the upper range than there should be within a normal distribution, and it's probably multi-modal but that's a conversation for another day). Worth a watch.