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Shortly after publication, Donald T. Campbell and Julian C. Stanley's Experimental and Quasi-Experimental Designs for Research on Teaching (1963) gained the status of a classic exposition of experimentation in education. There have been few attempts to extend this pioneering work, as might be expected of a work so comprehensive in conception and so brilliant in execution. Webb et al. (1966) produced a work similar in purposethat being to identify sources of external invalidity which arise from the reactive effect of measurement. We know of no other
Bracht et al. (Fri,) studied this question.
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