The method of specifically identifying clusters of related items on a test that measure a common ability is called

Factor analysis.

Explanation:

The key concept of this analysis method is seen that a lot of variables which are seen to have like terms and also variables are seen to worked on severally to produce the given output/result. It is known to be not a singular pattern but it is seen to have a family group pattern because of its involvement with multiple variables.  

It is also widely used in thesis researches and also dissertation like sometimes seen to be used in developing tests for psychological measurements etc.

dont understand question can you makeit more better

if you have to make a general question and respond to your thoughts, then this isn't really a question someone can you on. read the passage, form your question, and answer using your thoughts. no one else can understand how you interpreted this text if you don't tell us.