4) is actually funny because that is what you would expect if their search wasn't based on race. ie: if they were correctly using risk factors when deciding whether to search or not then the chance of finding contraband conditional on being searched should be the same. it even says this in the study:

    Though we found that African Americans were significantly more likely to be searched than Whites, this overall higher rate of searching did not result in a lower recovery rate as one would expect if officers were using lower standards to search African Americans, as other researchers have found in other cities