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Asia-Pacific Forum on Science Learning and Teaching, Volume 17, Issue 2, Article 2 (Dec., 2016) |
A quasi-experimental research design with a nonequivalent control group and a pretest-posttest was used in this study. The research was carried out with two groups--a study group and a control group. In the study group (Case-Based Group-CBG), the physics topics that were to be taught were treated using the Case-Based Learning approach. In the control group (Traditional Instruction Group-TIG), the same topics were treated using traditional instruction methods (in line with the 2013 Secondary School 9th Grade Physics Course Teaching Program). The research was conducted with students enrolled (n=60) in two different 9th-grade physics classes in an Anatolian Girls' Vocational High School located in the province of İzmir, Turkey. Because the guidelines to teaching and education at the schools were not conducive to creating new groups (since the conditions needed for a fully experimental research design could not be met), it was decided that an nonequivalent control group, pretest-posttest quasi-experimental research design would be used (Gay & Airasian, 2000). The independent variable in the study was the method of instruction that was used. The dependent variables were the students' scores on the Energy Conceptual Test (pretest and posttest).
Students at the school where the study took place were randomly assigned into two 9th grade classes at equivalent achievement status, which comprised the study (n=30) and the control groups (n=30). The study group was named the "Case-Based Group" and the other group, the "Traditional Instruction Group." All of the students in the study group were girls because the school was Girls’ School.
Energy Conceptual Test (ECT)
The Energy Conceptual Test (ECT) that the researchers drew up in line with the Secondary School 9th Grade Physics Course Teaching Program was used to determine which misconceptions students had about the subject of energy and to measure their conceptual understanding. The number of questions were distributed in accordance with the learning gains expected from the topics of "Work, Energy and Power, Mechanical Energy, Conserving Energy and Energy Conversion, Productivity, Energy Sources" contained in the Energy unit in the 9th grade physics course program.
As Treagust and Chandrasegaran (2007) suggest, the review of the students' conceptual changes was made with the use of multiple choice questions that would enable both qualitative and quantitative analysis and an additional number of open-ended questions concerning the topics mentioned above. The two-tier test developed in this study started out with a multiple-choice test of five choices. In the second tier, an open-ended answer was expected of the students as they were asked to explain the grounds for the choices they made in the first tier.
After the researchers constructed the conceptual test on the basis of 19 items, two physics teachers (with more than 10 years teaching experience) and three faculty members who were specialized in physics education were asked to check the test for content and visual validity. In line with the opinions of the specialists, two items in the test were eliminated because they were thought to be unsuitable for the conceptual test construct. The remaining 17 test items were declared appropriate for the 9th grade level as well as valid in terms of content and appearance. The test was tested for reliability in the province of İzmir at two high school 10th, 11th and 12th grade classes, encompassing a total of 131 students. The analysis of the test used the categories classified by Coştu and Ayas (2005). The scoring of the test in Table 1 was achieved by the evaluation of the data in both the first and second tiers. The categorization of the answers to the two-tier test was based on the following:
ü Right response-Right reason: Sound Understanding (SU)
ü Right response-Partially right reason or Wrong response-Right reason: Particular Understanding (PU)
ü Right response-Wrong reason, Right response-Blank or Wrong response-Partially right reason: Specific Misconception (SM)
ü Wrong response-Wrong reason, Wrong response-Blank or Completely Blank: No Understanding/No Response (NU/NR)Table 1. The evaluation criteria used in assessing the two-tier open-ended questions
Levels of Understanding
Explanation
Assessment Criteria
Scores
Right reason
Responses that contain all aspects of valid reasons
right response-right reason
wrong response-right reason3
2Partially right reason
Responses that do not contain all aspects of valid reasons
right response-partially right reason
wrong response-partially right reason2
1
Wrong reason
Responses that contain incorrect information
right response-wrong reason
wrong response-wrong reason1
0Blank
Irrelevant, unclear response or leaving blank
right response-leaving blank
wrong response-leaving blank
leaving completely blank1
0
0Explanatory factor analysis was performed to determine the factor construct of the test. Because of a low item-test correlation (item discrimination index) on a revised item on the ECT (r=0.007) and also since the first factor analysis yielded a negative value, it was decided that this item would be removed from the conceptual test. The remaining 16 items after one item was removed showed in the new factor analysis that the eigenvalue of the test items were collected in 4 dimensions greater than 1. These 4 dimensions explained 53.58% of total variance.
After construct validity, as part of the reliability study for the ECT, the instrument's Cronbach Alpha coefficient was calculated to define internal consistency. The reliability coefficient for the whole test is 0.784. According to Büyüköztürk (2011), for a conceptual test to be reliable, it is considered adequate for the Cronbach Alpha coefficient for the entire test to be 0.70 or greater (e.g., Samsudin et al., 2016). In the light of this information, it may be said that the Energy Conceptual Test developed for Energy topics is a valid and reliable measurement tool. A sample question contained in the test is presented in Appendix A.
Learning Materials
In the teaching process in this project, Case Stories were used in the Case-Based Group while in the traditional instruction group, the learning materials recommended in the High school 9th grade physics textbook published by the Turkish Ministry of National Education Head Council of Education and Morality were employed. The teaching materials have been described in detail below.
In this project, 8 case story scenarios were prepared for use in the case story teaching method addressing the 9th grade Physics Energy Unit topics of Work, Energy and Power, Mechanical Energy, Conservation of Energy and Energy Conversion, Efficiency, Energy Sources. These texts, which were developed by the researcher (who had 5 years of experience in physics teaching), were devised to suit the 9th grade level and the curriculum.
To ensure that the case story scenarios were appropriate for the level of the students and the curriculum (in terms of both scope and educational gains), the views of specialists (an experienced physics teacher and a faculty member specialized in physics education) were enlisted and the scenarios were revised in the direction of the feedback from these specialists. Later, a pilot run was performed with a similar student group outside of the study group; no problem was encountered with the scenarios during this pilot experiment.
The scenarios developed presented a real-life situation or a slice of life. The scenarios that were devised were written out on a worksheet and supported with videos (case stories presented online) and illustrations. Each scenario was given a heading that reflected the essence of the story. Also, the stories were supported with questions that sought to develop students' thinking skills and thus ensure integration with the theoretical dimension. The characteristics of the group, their times and gains were reviewed and the single session "Short Story-Based Learning" (Waterman and Stanley, 1998), then the "Direct Story-Based Learning" (Waterman and Stanley, 1998) session where questions began to be asked, and the "Abridged Case Stories" (Sönmez, 2005) generally limited to one paragraph were implemented. Some existing stories were taken from the newspapers and the Internet but names were deleted to avoid harming real persons and organizations. The scenarios were developed to follow a discussion format that was appropriate for a small group. Meanwhile, because the scenarios are written out on a worksheet, they may be passed out to students as homework. One of the case stories is presented in Appendix B.
The research was conducted in the spring semester of the 2013-2014 academic year and involved the unit of "Energy" in the 9th grade physics course. The duration of the study was a total of 6 weeks. Both groups were administered an "Energy Conceptual Test" as a pretest and a posttest before and after the implementation of the experiment. The study experiment was initiated immediately after the pretesting.
Treatment in the Case-Based Group
The first lesson in the Case-Based Group was geared to introduce the method of Case-Based Learning and how this would be handled with a short case story about Newton's Law of Inertia in a worksheet entitled "A Ride on the City Bus." In all the other lessons, the Case-Based Group was arranged in the classroom in 6 groups of 5 students each. Teaching the topics using the case story scenarios started with the distribution of the worksheets containing the case stories. Each student received a worksheet. The students were first asked to read through the text of the case story. Then the students were asked to make use of the resources they brought to class (textbooks and other helpful references) to answer the open-ended questions they found right below the texts of the case stories. The researcher walked around the groups at this time to help the students use their resources and guide them in how they might be more efficient in this. At the same time, the researcher gave the students clues about how they could find the right answers, without actually correcting their mistakes. After the students finished answering the questions, the group spokespersons were asked one by one to come to the board and read out the answers to each question. After this was completed, the students were given the opportunity to hold a short discussion about each question. The teacher also participated in the discussions. Ultimately, after the incorrect answers were found with help from the teacher, a student secretary was asked to write down the best answers on the board. The same process was repeated for the other questions as well. At the next class, the students were presented with a new case story. The sample problems solved in the Traditional Instruction Group were solved together with the students in the Case-Based Group.
Treatment in the Traditional Instruction Group
In this group, the teaching remained loyal to what was offered in the Physics 9 Textbook published by Turkish Ministry of National Education (2013). The lecture method and question and answer technique were used in the TIG. It was the teacher who played a more active role over the course of the session than the students. As the topics were taken up, discussions were held with the students. At the end of each topic, sample problems were solved together with the students.
All the data obtained from the Energy Conceptual Test were analyzed using the SPSS 15.0 program. The data collected from the research were analyzed using frequencies (f), percentages (%), arithmetic means (M), and standard deviation (SD).
