Experimental methods have a discrete place due to their effectiveness to establish cause-effect relationship and, to make manipulations and to provide control over the variables. Although majority of the science education dissertations in Turkey involve experimental studies, lack of sound experimental designs to control validity threats is still an important problem. And also, there is a need to conduct school-wide experiments to test effectiveness of methods and techniques or other reform

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... rements in science education. These experiments need more comprehensive and powerful research designs to overcome problems about internal validity threats. This study purposes to suggest a new, more comprehensible design of experimental study. Five-group experimental design has been suggesting, by controlling more threats to internal validity, a more sound way to establish cause-effect relationship and to control more variables which are potentially effective on dependent variables of the science education studies.