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our discussion of researcher effects, we drew attention to the negativeconsequences of researcher orientation effects, and particularly to thoseassociated with researcher expectation effects. The chances of obtainingaccurate observations are increased when, for example, interviewers are givenclear instructions as to the aims of the project, the importance of accurateinterviewing is emphasized, or the need for consistent interviewing is madeclear. Thorough pre-training is also likely to eliminate or reduce the occurrenceof some of the other researcher effects that we have not mentioned, such as theinaccurate noting of responses, coding errors, classification errors, and manymore.SELECTION OF FIELD WORKERSThe origin of one of the most important researcher effects is to be found in thedistance between researchers and participants. Although different factors, suchas context or level of motivation, result in greater degrees of distance betweenresearchers and participants, researcher characteristics such as gender, race,age and style of dress, are some of the most important factors that fall underthis rubric. An obvious solution to this problem is to exercise due care in theselection of field workers. Those field workers who share as manycharacteristics of the sample as possible (like gender and race, for example)ought to be given preference.Free download from www.hsrcpress.ac.zaRELIABILITY OF MEASURING INSTRUMENTSIn the case of structured measuring instruments such as scales andpsychological tests, a number of standard techniques are available by means ofwhich reliability may be estimated. Four of the better known techniques are (i)the use of parallel forms, (ii) the test-retest method, (iii) the split-half method,and (iv) the method of internal consistency. Any standard text in the field ofmeasurement theory (for example Carmines & Zeller, 1979) and test theory(see Nunnally, 1964, 1978) would include a discussion of these techniques.The aim of techniques of this nature is to determine the reliability of measuringinstruments, and specifically the extent to which the particular scale or test islikely to yield the same measurements upon repeated application.In those cases where these methods are not applicable, the researcher could stillmake use of pilot studies to test the items or the observation categories that areto be employed. Excessive variance or large numbers of non responses could,for example, either be an indication that the items are ambiguous or that theyare unusually sensitive. The major importance of pretesting, and the use ofmethods such as those mentioned earlier, is that they enable the researcher todetermine the most important measuring instrument effects, and to eliminatethem.95