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67 GLOSSARY Ability test--A test that measures the current performance Construct validity--The degree to which a measure of a or estimates future performance of a person in some specific personal characteristic (e.g., constructs such as defined area of cognitive, psychomotor, or physical func- "mental ability," "impulsivity," and "agreeableness.") is tioning (DOL 2000). known to be relevant to the performance of a job. Adverse impact--A situation in which members of a par- Content validity--The degree to which the content of a test ticular race, sex, or ethnic group have a substantially corresponds to the knowledge or behavior content of a lower rate of selection in hiring, promotion, or other job. For example, an on-road assessment has high content employment decisions (DOL 2000). validity in relation to on-the-job driving. Assessment--Any test or procedure used to measure an Correlation--The degree of association or predictability individual's employment or career-related qualifications between two variables within the same group of subjects or characteristics (DOL 2000). (e.g., drivers). Examples include the correlation between sets of test scores, or between test scores and job perfor- Associated factors (e.g., in the LTCCS)--Human, vehicle, mance measures. or environmental conditions present at the time of the crash. Associated factors are not direct crash causes but Correlation coefficient--A statistic summarizing direction are often viewed as contributing factors. and degree of association. Correlation coefficients range from -1.0 (a perfect inverse relation) through zero (no Attitude --An individual's positive or negative evaluations statistical association) to +1.0 (a perfect linear relation). of a particular thing (person, topic, country, activity, etc.). Most important here are attitudes toward driving Criterion--Any measure of work behavior or any outcome behaviors. Attitudes have cognitive (knowledge, belief) that can be used as the standard for successful job perfor- and emotional components, and are reflected in behav- mance. Relevant examples include driver crash rate, vio- iors. Safety-related attitudes are persistent and thus are a lation rate, tenure with company, or supervisory ratings potential basis for driver selection. On the other hand, of performance as a driver. attitudes may change based on new knowledge, experi- Criterion-based validity--The degree to which test scores ence, and maturation. correlate with actual job performance criteria. Includes Attribution bias --The strong tendency of most people to predictive validity (predicting future performance) and attribute their own behavior to situational factors while concurrent validity (correlates with current performance). attributing the behavior of others to internal factors (e.g., Critical Reason (CR) --In the LTCCS, the human, vehicle, their character, personality, abilities). or environmental failure leading to the critical event and Basic skills tests--Assessments of competence in reading, thus to the crash. The immediate or proximal cause of a simple mathematics, and other skills that are widely crash. required in training and employment settings (DOL 2000). Differential driver risk--Persistent individual differences Biodata--Information on personal characteristics, including among drivers in crash risk. Related to various personal physical, medical, and behavioral history information. traits such as age, personality, character, medical condi- tions, other physical variations, and performance Chronotype --A person's fatigue susceptibility and sleep- capabilities. and alertness-related characteristics. Although the same general factors affect people's alertness levels, there are Inventory--A questionnaire or checklist that elicits infor- also significant individual differences, especially in vul- mation about an individual in such areas as work values, nerability to drowsiness. interests, attitudes, and motivation (DOL 2000). Construct--A concept or explanatory label for a personal Job analysis--Defining and describing a job in terms of the characteristic that is not directly observable or that can- behaviors necessary to perform it. Includes job tasks and not be captured by a single observation or measure. For knowledge, skills, and attitudes necessary for successful example, people skillful in reasoning and complex performance. thought are considered high on the construct mental abil- Mean--The arithmetic average score in a group of scores, ity. Mental ability is not directly visible, but its manifesta- computed by adding all the scores and dividing the sum tions and its significance for occupational success are by the number of cases. easy to recognize.

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68 Median--The middle score in a group of scores. The point Selection success ratio --Conceptually, the percentage of or score that divides the group into two equal parts. Also correct decisions made in hiring. Specifically, this is the known as the 50th percentile. sum of the correct acceptances (hired employees who perform well) and correct rejections (nonhired who Multiple-hurdles approach--An approach to personnel would have performed poorly) divided by all applicants. assessment that requires a candidate to pass all tests in In practice, the success ratio cannot be calculated, but it sequence in order to qualify (DOL 2000). is a useful concept for understanding employee Normal distribution--The "bell-shaped curve" character- selection. izing the distribution of many human traits such as height Sensitivity (test) --The ability of a test to correctly identify (within either gender), IQ score, and manual dexterity. and reject unsafe or otherwise unsatisfactory drivers. In Driver risk is not normally distributed. other words, the probability of driver failure in a criterion Normative score --A test score stated in relation to a peer measure (e.g., on the job) given a test prediction of group; for example, a percentile score in relation to other failure. commercial drivers (DOL 2000). Skewed distribution--A lopsided distribution in which Norms --Descriptive statistics that are used to summarize there are more individuals at one end than the other. This the test performance of a specified group, such as a sam- is contrast to the normal distribution or "bell-shaped ple of workers in a specific occupation. Norms are often curve," which is symmetrical with most people in the assumed to represent a larger population, such as all middle. For drivers in general and within almost any sub- workers in an occupation (DOL 2000). group (e.g., a fleet), there are typically many relatively low-risk drivers, some drivers of medium risk, and a few Odds ratio --A statistic often used to quantify relative risk drivers of much higher risk. or occurrence of an outcome for two different situations or groups. An odds ratio greater than 1.0 implies overin- Specificity (test) --The ability of a test to correctly identify volvement (e.g., in driving incidents), whereas an odds and accept safe or otherwise satisfactory drivers. In other ratio less than 1.0 implies underinvolvement. words, the probability of driver success in a criterion measure (e.g., on the job) given a test prediction of Percentile score --The score on a test below which a given success. percentage of scores fall. For example, a score at the 65th percentile is equal to or higher than the scores obtained Standard deviation--A statistic used to describe the vari- by 65% of the people who took the test (DOL 2000). ability within a set of scores. It indicates the extent to which scores vary around the mean or average score. Personality--Individual behavioral or psychological con- sistency over time and across different types of situa- Standardized test--A test developed using professionally tions. Style of interaction with other people and life prescribed methods which provides specific administra- situations. Examples include aggressiveness, impulsivity, tion requirements, instructions for scoring, and instruc- sensation-seeking, extraversion-introversion, conscien- tions for interpreting scores (DOL 2000). tiousness, and agreeableness. Test--Any instrument or procedure that samples behavior Reference group --The group of individuals used to develop or performance. A personnel or employment test is the a test; for example, commercial drivers, commercial general term for any assessment tool used to measure an drivers meeting some performance criterion. individual's employment qualifications, capabilities, or characteristics (DOL 2000). Reliability--The degree to which test scores are consistent, dependable, or repeatable. Traits vs. states --Traits are enduring personal characteris- tics (e.g., medical conditions, personality), whereas states Reliability coefficient--A correlation coefficient indicating are temporary characteristics (e.g., short illness, moods) the degree to which two sets of test scores are associated that may reflect recent events. or repeatable. Validity--The degree to which an assessment actually mea- Risk factor--Any prior factor--driver, vehicle, environ- sures what it purports to measure. A test's validity is mental, carrier--that affects the probability of a crash. determined in contexts such as content validity, construct Risk perception--A complex cognitive process represent- validity, and criterion-based validity (predictive or ing the level of perceived risk that drivers use to calibrate concurrent). their risk-taking behaviours (Thiffault 2007). Validity coefficient--A numeric index that shows the Selection ratio --In hiring, the ratio of job hires to job appli- strength of the relationship between a test score and a cants. Other factors being equal, a low selection ratio (i.e., criterion, such as job performance. Expressed as a cor- more selective hiring) results in higher average on-job relation between predictor(s) and job performance, and performance of new hires. sometimes called a V-score.