Bell Curve

280 The National Context Ethnic Differences in Cognitive Ability 28 1people represented in the NLSY. This figure shows why a B/W differencecan be problematic to American society as a whole. At the lowerend of the IQ range, there are approximately equal numbers of blacksand whites. But throughout the upper half of the range, the disproportionsbetween the number of whites and blacks at any given IQ levelare huge. To the extent that the difference represents an authentic differencein cognitive functioning, the social consequences are potentiallyhuge as well. But is the difference authentic?Are the Differences in Black and White Scores Attributable to CulturalBias or Other Artifacts of the Test?Appendix 5 contains a discussion of the state of knowledge regardingtest bias. Here, we shall quickly review the basic findings regardingblacks, without repeating the citations in Appendix 5, which we urgeyou to read.EXTERNAL EVIDENCE OF BIAS. Tests are used to predict things-mostcommonly, to predict performance in school or on the job. Chapter 3discussed this issue in detail. You will recall that the ability of a test topredict is known as its validity. A test with high validity predicts accurately;a test with poor validity makes many mistakes. Now supposethat a test's validity differs for the members of two groups. To use a concreteexample: The SAT is used as a tool in college admissions becauseit has a certain validity in predicting college performance. If the SAT isbiased against blacks, it will underpredict their college performance. Iftests were biased in this way, blacks as a group would do better in collegethan the admissions office expected based just on their SATs. Itwould be as if the test underestimated the "true" SAT score of the blacks,so the natural remedy for this kind of bias would be to compensate theblack applicants by, for example, adding the appropriate number ofpoints onto their scores.Predictive bias can work in another way, as when the test is simplyless reliable-that is, less accurate-for blacks than for whites. Supposea test used to select police sergeants is more accurate in predicting theperformance of white candidates who become sergeants than in predictingthe performance of black sergeants. It doesn't underpredict forblacks, but rather fails to predict at all (or predicts less accurately). Inthese cases, the natural remedy would be to give less weight to the testscores of blacks than to those of whites.The key concept for both types of bias is the same: A test biased againstblacks does not predict black performance in the real world in the same waythat it predicts white performance in the real world. The evidence of bias isexternal in the sense that it shows up in differing validities for blacks andwhites. External evidence of bias has been sought in hundreds of studies.It has been evaluated relative to performance in elementary school,in secondary school, in the university, in the armed forces, in unskilledand skilled jobs, in the professions. Overwhelmingly, the evidence isthat the major standardized tests used to help make school and job decision~'~~~do not underpredict black performance, nor does the expertcommunity find any other general or systematic difference in the predictiveaccuracy of tests for blacks and whites.'2H1INTERNAL EVIL~ENCE OF BIAS. Predictive validity is the ultimate criterionfor bias, because it involves the proof of the pudding for any test.Rut although predictive validity is in a technical sense the decisive issue,our impression from talking about this issue with colleagues andfriends is that other types of potential bias loom larger in their imaginations:the many things that are put under the umbrella label of "culturalbias."The most common charges of cultural bias involve the putative culturalloading of items in a test. Here is an SAT analogy item that hasbecome famous as an example of cultural bias:RUNNER:MARATHON(A) envoy:embassy(B) martyr:massacre(C) 0arsman:regatta(D) referee:toumament(E) horse:stableThe answer is "oarsman:regattaW-fairly easy if you know what both amarathon and a regatta are, a matter of guesswork otherwise. How woulda black youngster from the inner city ever have heard of a regatta? Manyview such items as proof that the tests must be biased against peoplefrom disadvantaged backgrounds. "Clearly," writes a critic of testing,citing this example, "this item does not measure students' 'aptitude' orlogical reasoning ability, but knowledge of upper-middle-class recreationalactivity."'2" In the language of psychometrics, this is called internal