Three studies investigated causal reasoning when 2 dispositions-one more common than the other-are both consistently associated with a behavior. Subjects rated the rare disposition as the more important cause when the behavior itself was rare but violated the covariation principle by rating the common disposition as more important when the behavior was relatively common. Results suggest that use of the covariation principle may be the most important heuristic for inferring causality only when the action to be explained is relatively rare. When the behavior is a common one, causal attributions may be more influenced by a principle of generative strength, with observers assigning greater causal importance to the disposition they believe to be stronger.As Kahneman and Varey (1990) have noted, the study of causality has traditionally been approached from two very different perspectives. The dominant view in both psychology and philosophy has antecedents in the writings of Hume (1739/ 1964) and Mill (1872. This perspective treats causality in terms of probability, as a contingent relation between events. For example, Mill proposed that a factor is designated a cause if it is present when the effect is present and absent when the effect is absent (i.e., the method of difference). Within psychology, Mill's proposals have a close affinity with the views of Kelley (1967), who suggested that the naive attributor tends to base causal attributions on a principle of covariation.From McArthur (1972) on, the bulk of empirical evidence in social psychology has indicated that attributions are in fact frequently covariation based. Recently, Fosterling (1989) has suggested that extensions and refinements of the Kelley model (e.g., Hewstone & Jaspars, 1987;Hilton & Slugoski, 1986;Pruitt & Insko, 1980) can be unified within an analysis of variance (ANOVA) framework, and Cheng and Novick (1990Novick ( , 1991Novick ( , 1992 have proposed a probabilistic extension of the ANOVA analogy. These investigators offered impressive evidence that, at least when people are given sufficient information, causal attributions are indeed determined by covariation.Despite the support for a covariation-based explanation of

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Today modern epoxy base materials for printed circuit board production are designed with properties which ensure high dimensional stability, resistance to chemical action, and increased glass transition temperature, in order to meet the stringent demands now encountered in electronics use. Polyfunctional epoxy resins and the appropriate hardener/accelerator compositions are in widespread, effective use in the design of superior laminates. The quality of the through‐hole plating for holes drilled in these improved materials will depend on various parameters, including those covered by three main complexes: base material, mechanical processing, and chemical processes used for treatment of the drilled hole. Special attention is paid in this paper to the resin recession phenomenon in terms of processing parameters.

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