The extent to which discovery and inquiry activities need to be structured depends somewhat on students current knowledge and reasoning skill. For instance, advanced high school science students many profit from their own, self-directed experiments if they can test various hypotheses systematically through careful separation and control of variables and if they have appropriate concepts (force, momentum, etc.) with which to interpret their findings. Younger and less knowledgeable students are apt to need more guidance about how to design conclusive experiments and interpret their findings (de Jong & van Joolingen 1998; D. Kuhn & Pease, 2010; B.Y.White & Frederiksen, 2005;Aohar & Aharon-Kraversky,2005)