ABSTRACT. 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 requirements 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.
Keywords: Creative thinking, critical thinking, academic achievement, science process skills