Document peeqj6Z33pvvL0LdR0Mebn8X7

11--Human Behavior and Safety dimension is increased, the other dimension also increases Because the number deals with the magnitude of relationship, a reliabil ity of -- 60 is greater in magnitude than a coefficient of + 45, although the variables are inversely related in the former Although it is theoretically possible to have a reliability coefficient as low as --1 00, m practice the value rarely goes below + 20 How high can a coefficient be? This is diffi cult to answer, since the answer depends upon the use of the testing instrument, the nature and manner in which reliability was obtained, and other factors Validity refers to the test's or instrument's power or ability to measure what it is intended to measure--the degree of correlation the instrument has with the external criterion it is supposed to measure Once again validity is expressed as a correlation coefficient A negative sign, however, is as useful as a posi tive coefficient A negative validity indicates that those possessing more of the measured trait are less desirable An illustration might be testing for a job that requires very little mental ability--it may be negatively corre lated with an IQ test so that the desirable workers for the job are those with the lower test scores A measurement may be reliable without being valid, but a valid measurement must also be reliable Because reliability is self correlation and validity is a correlation with some external criteria, a test cannot be corre lated with something else and. not correlate with itself To illustrate that a reliable meas ure may not also be valid, consider a yardstick A yardstick is very reliable--it gives a con sistent measurement every time it is used It is also valid for measuring the length of a table But if a yardstick is used for weighing the table, it is no longer valid for measuring In addition to reliability and validity, a measuring technique must be practical A technique mav possess high validity but be so cumbersome and intncate that it can only be used in special situations, and then only by highly skilled technicians In spite of its statistical value, such a technique is almost worthless Two sampling techniques used for eval 244 uating potential accident-producing behavior are (a) the critical incident technique, de scribed in Chapter 4, and (b) behavior sampling The behavior sampling or activity sampling technique involves the observation of worker behaviors at random intervals and the instan taneous classification of these behaviors ac cording to whether they are safe or unsafe Calculations are then made to determine either (a) the percent of time the workers are in volved in unsafe acts or (b) the percent of workers involved in unsafe acts during the ob servation period Various components of a safety program (le, safety lectures, posters, 5-minute safety talks, safety inspections, mo tion picture films, supervisory training) can be applied and an immediate indication of their influence on unsafe behavior can be obtained It is important that the safety professional approach any psychological evaluation with caution Texts and references in industrial, social, and personnel psychology will provide guidelines for the development and use of test batteries for measuring individual dif ferences These tests or evaluative instru ments are best developed and administered by competent professionals who specialize m this work With respect to the problem of screening employees or potential employees in regard to then accident potential, caution must be exer cised To date, no systematic screening pro cedures have been developed which meet both reliability and validity criteria and which are adequate for use in all industries or even m a specific industry While in theory such a screening procedure is possible, the state of scientific knowledge in occupational safety re search is too limited to support the develop ment of such screening measures Motivation Through the interaction of hereditary and environmental factors, each worker is an in dividual personality The safety professional must be continually aware of individualities when dealing with human beings There are instruments by which various aspects of human behavior can be evaluated, many of which are already in use in industry