The language in that description refers to "protected groups". As long as the author is not calculating selection rates for groups of candidates based on some special criteria, such as race, gender, age, etc. he should be ok, right?
"adverse impact" is designed to sniff out hiring criteria that are a proxy for discrimination based off criteria such as race, gender, and age.
For instance, if you selected for college graduates for hiring firefighters, and that causes a lot of rejected applications among African American candidates, then it would be illegal based off of an adverse impact against a protected group.
As an aside, suing employers over requiring a college degree is a seriously under-tapped and under-estimating way to charitably improve the lives of Americans (college is a positional good because college matters when employers are looking at candidates - if employers can't look at whether or not you have a college degree unless it's a bona-fide qualification, then many more people don't have to spend several years and tens of thousands of dollars)
That's not nearly enough. The 4/5ths rule is designed to identify "structural discrimination", or cases where no discriminatory act can be identified, but the outcomes are nonetheless considered discriminatory. As long as a lawyer can show that some protected group is disadvantaged by the quiz, that's enough for it to violate the rule.
I am not a lawyer, but I thought the defence was if you can show that the screening criteria correlated with on the job performance it is OK. No matter what you think of protected groups using a criteria that does not correlate with performance is not very smart anyway.
There may be some certification process you can go through to get a test approved, but mere job applicability isn't enough. For example, this firefighting test was found to violate the 4/5ths rule.
