Speaking as someone whose exposure to intelligence testing comes second-hand via a psychology graduate student, my understanding is that the quality of an IQ test is just based on how well it correlates with other IQ tests. The distribution always looks normal because they normalize it. https://en.wikipedia.org/wiki/G_factor_%28psychometrics%29#P...
We may not understand what intelligence is philosophically, but in the field of psychology, IQ/general intelligence/g factor is a statistical construct that isn't directly measurable but can be inferred by its correlation with measurable factors. https://en.wikipedia.org/wiki/Factor_analysis
We may not understand what intelligence is philosophically, but in the field of psychology, IQ/general intelligence/g factor is a statistical construct that isn't directly measurable but can be inferred by its correlation with measurable factors. https://en.wikipedia.org/wiki/Factor_analysis