Sentence:  The <WSD>relationship</WSD> of intelligence test scores to school achievement is a well established fact ( in this case , * * f ) ; therefore , in the investigation of the present hypothesis , it was necessary to control this factor . 
Meaning of the word marked with <WSD> tags:  a relation between people; (`relationship' is often used where `relation' would serve, as in `the relationship between inflation and unemployment', but the preferred usage of `relationship' is for human relations or states of relatedness)