Grade 10 Physical Science Learners’ Understanding and Application of Concepts of Evidence in Experimental Design

[摘要] One of the most important challenges of the secondary school science teacher is to helplearners to obtain, analyze and evaluate evidence using experimental and investigativemethods. The understanding and application of concepts of evidence play a central role insetting up valid experiment and is usually ignored in the secondary school sciencecurriculum. Recognizing the significance and value of an understanding of evidence indeveloping learners’ ability to carry out appropriate experimental work in science, thequestion arises of learners’ understanding of 'concepts of evidence’ in experimentaldesign. In this study the researcher endeavored to answer some of the questionsconcerning learners’ understanding of evidence: What understanding do learners enteringthe Further Education and Training (FET) band have of the concepts of validity inexperimental design? What is the effect of an intervention on their understanding ofconcepts of validity? How well do learners show their ability to apply concepts ofevidence to an assessment task?The study investigated the ability of a sample of grade 10 Physical Science learners, inone Gauteng Province secondary school to use and understand the concepts of evidencebefore and after an intervention, and their ability apply these ideas about evidence in anassessment sheet task. First, a survey of learners’ understanding of the concepts ofvalidity was conducted using a written diagnostic test, consisting of three probes that hadbeen previously used to diagnose learners’ understanding of validity in experimentaldesign. Second, an evaluation of changes in such understanding due to a specific teachingintervention was completed using the same diagnostic test. Finally, the 2004 Grade 9Common Tasks for Assessment (CTA) investigation task was administered to the samesubjects in order to investigate whether or not their understanding of concepts ofevidence would be apparent in this CTA investigation task.Several key findings emerged from the data. The major findings of this study were thatthe sample investigated began the study with a level of understanding equal to a group ofFoundation University students tested in a previous study and that their understanding didnot change much during the intervention. In fact, analysis of the results from the probesin the diagnostic test revealed that learners had little problem choosing the independent variable and controlling variables. However, the findings from the probes indicated thatthe intervention did not seem to have had a major effect since the difference in thenumber of responses between the pre-test and post- test was relatively small. Moreover,the results also revealed that it was possible to analyze learners’ responses using theexisting model of learners’ understanding of validity, and that the majority of learners fellinto Level C in the model which refers to the application of previous understanding in anew situation.The results from the CTA investigation task revealed that learners’ understanding ofconcepts of evidence could be demonstrated in new science context. In fact, the resultsrevealed that learners showed ability to apply their understanding of concepts of evidencein experimental design to the assessment task. Moreover, the CTA results indicated thatthe understanding of identifying variables, constructing graphs; describing therelationship between variables in a graph; formulating the investigative questions werethe most applied concepts of evidence by learners. Finally, the results of this studyhighlight the need for providing secondary science learners with opportunities to practiceand develop concepts of evidence. In the light of these findings it is recommended thatchildren need to be explicitly taught about the purpose of science investigations andintroduced to important ideas about evidence if their ability to perform investigation tasksis to be improved.

[发布机构] University of the Witwatersrand