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earlier, the strengths of the randomized controlled trial are contrasted by a number of considerations (feasibility, practicality, ethics), so this design involves a number of decisions that frequently limit its use.

PATTERN OF EVIDENCE COMPARISONS

Results across the variety of datasets are also summarized in this report using the “pattern of evidence” approach. This is an alternative approach to analyzing a collection of datasets, contrasted with the traditional approach of “preponderance of evidence,” which by strict definition is reserved for summarizing a larger body of studies with more uniform research designs. Rather than summarizing the results of studies to determine whether the direction and magnitude of association is similar across studies to develop a preponderance of evidence, the pattern of evidence approach looks at the extent to which results from one class of studies help to compensate for the limitations from another class of studies. The goal is to establish a pattern of evidence that can be discerned from multiple data sources that are based on different sampling frames and methods.

This approach considers interrelated conditions, such as intermediate outcomes (e.g., if there is a reduction in back disorders after the implementation of job redesign), and can be used to decide whether there are other pieces of evidence available to rule in its plausibility (Cordray, 1986). For example, such evidence could include: epidemiologic evidence that shows an association of repetitive lifting and back disorder among different occupational groups, independent of organizational, psychological, and recreational factors; biomechanical literature showing precise load location, load moment, spinal load, three-dimensional trunk position, frequency, and kinematics that points to a well-defined pathway for exposure and risk of spine structure loading; and basic biological studies showing that a greater magnitude of spinal loading can explain deterioration of spinal tissue and can cause damage. Thus, the more supportive the pattern of evidence, the more plausible the perceived effect. The strength of this method is that, alone, self-reports of work practices in epidemiologic studies might be important but could be questioned as being subject to socially desirable responding; having data from other sources helps to strengthen inferences that this behavior occurred. Similarly, having a reduction in back disorders after implementing job redesign could be due to any number of factors, but having data to show that there was a decrease in specified biomechanical actions at the level of the individual bolsters confidence that the observed results might be due to the intervention. Of course, there can be inconsistencies, such as no change in the frequency of back disorder in a workplace where a program was implemented. However, further investigation might show that the program, while well in-



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