Which statistical method is used to identify clusters of related items on a test?

Factor analysis is a statistical method used to identify clusters of related items on a test by examining the correlations between various variables. This approach helps researchers and psychologists recognize underlying factors that explain observed patterns in data, such as test responses. By grouping test items that correlate highly with each other, factor analysis can uncover dimensions or constructs that the items may be measuring collectively, which is particularly useful in the development and validation of psychological assessments.

In the context of intelligence testing, factor analysis can reveal the different aspects of intelligence, such as verbal reasoning, spatial ability, and quantitative skills, highlighting how these domains interrelate. This makes it an essential tool for psychologists in understanding the structure of intelligence and improving the design of tests to ensure they accurately measure what they intend to.