Bell Curve

678 Notes to page 74 Notes to pages 74-76 679studies than the column for job proficiency. Regarding job performance,one major study evaluated the performance of about 1,500 air force enlistedmen and women working in eight military specialties, chosen to berepresentative of military specialties in the air force. Performance was variouslymeasured: by defining a set of tasks involved in each joh, then traininga group of evaluators to assess those specific tasks; by interviews of the~ersonnel on technical aspects of their jobs; by supervisor ratings aftertraining the supervisors; and combinations of methods. The average correlationbetween AFQT score and a hands-on job performance measurewas .40, with the highest among the precision measurement equipmentspecialists and the avionics communications specialists and the lowestamong the air traffic control operators and the air crew life support specialists.Insofar as the jobs were restricted to those held by enlisted men,the distribution of jobs was somewhat skewed toward the lower end of theskill range. We do not have an available estimate of the validity of theAFQT over all military jobs.Hartigan and Wigdor 1989.It is one of the chronically frustrating experiences when reading scientificresults: Two sets of experts, supposedly using comparable data, come outwith markedly different conclusions, and the reasons for the differences areburied in technical and opaque language. How is it possible for a laypersonto decide who is right? The different estimates of mean validity of theGATb.45 according to Hunter, Schmidt, and some others; .25 accordingto the Hartigan committee-is an instructive case in point.Sometimes the differences really are technical and opaque. For example,the Hartigan committee based its estimate on the assumption that thereliability of supervisor ratings was higher than other studies assumed-.8instead of .6 (Hartigan and Wigdor 1989, p. 170). By assuming a higher reliability,the committee's correction for measurement error was smallerthan Hunter's. Deciding between the Hartigan committee's use of .8 as thereliability of supervisor ratings instead of the .6 used by Hunter is impossiblefor anyone who is not intimately familiar with a large and scattered literatureon that topic, and even then the choice remains a matter ofjudgment. But the Hartigan committee's decision not to correct for restrictionof range, which makes the largest difference in their estimates ofthe overall validity, is based on a much different kind of disagreement.Here, a layperson is as qualified to decide as an expert, for this is a disagreementabout what question is being answered.John Hunter and others assumed that for any job the applicant pool 1sthe entire U.S. work force. That is, they sought an answer to the question,"What is the relationship between job performance and intell~gence forthe work force at large!" The Hartigan committee ohjected to their as-sumption on grounds that, in practice, the applicant pool for any partlcularjob is not the entire U.S. work force hut people who have a chance toget the job. As they accurately noted, "People gravitate to jobs for whichthey are potentially suited" (Hartigan and Wigdor 1989, p. 166).But embedded in the committee's objection to Hunter's estimates is atacit switch in the question that the analysis is supposed to answer. TheHartigan committee sought an answer to the question, "Among those peoplewho apply for such-and-such a position, what is the relationship betweenintelligence and job performance!" If one's objective is not todiscourage people who weigh only 250 pounds from applying for johs astackles in the NFL, to return to our analogy, then the Hartigan committee'squestion is the appropriate one. Of course, by minimizing the validityof weight, a large number of 150-pound lineman may apply for the jobs.Thus our reasons for concluding that the assumption used by Hunter andSchmidt (among others), that restriction of range calculations should bebased on the entire work force, is self-evidently the appropriate choice ifone wants to know the overall relationship of IQ to job performance andits economic consequences.23. The ASVAB comprises ten subtests: General Science, Arithmetic Reasoning,Word Knowledge, Paragraph Comprehension, Numerical Operations,Coding Speed, Auto/Shop Information, Mathematics Knowledge,Mechanical Comprehension, and Electronics Information. Only NumericalOperations and Coding Speed are highly speeded; the other eight arenonspeeded "power" tests. All the armed services use the four MAGE composites,for Mechanical, Administrative, General, and Electronics spedcialties, each of which includes three or four subtests in a particularweighting. These composites are supposed to predict a recruit's trainabilityfor the particular specialty. The AFQT is yet another composite fromthe ASVAB, selected so as to measure g efficiently. See Appendix 3.24. About 80 percent of the sample had graduated from high school and hadno further civilian schooling, fewer than 1 percent had failed to graduatefrom high school, and fewer than 2 percent had graduated from college;the remainder had some post-high school civilian schooling short of a collegedegree. The modal person in the sample was a white male between 19and 20 years old, but the sample also included thousands of women andpeople from all American ethnic groups; their ages ranged from a minimumof 17 to almost 15 percent above 23 years (see Ree and Earles 1990b).Other studies, using educationally heterogeneous samples, have in factshown that, holding AFQT constant, high school graduates are more likelyto avoid disciplinary action, to be recommended for reenlistment, and tobe promoted to higher rank than nongraduates (Office of the AssistantSecretary of Defense 1980). Current enlistment policies reflect the inde-