Scaffolding students’ experimental work with scientific abilities rubrics

1. Scaffolding students’ experimental work with scientific abilities rubrics Maria Ruibal Villasenor, Sahana Murthy, Anna Karelina and Eugenia Etkina Rutgers University, New Jersey http://paer.rutgers.edu/scientificabilities Supported by NSF grant DUE-0241078

2. One of the goals of the Rutgers PAER group is the development of a curriculum for the introductory physics courses taken by science majors.Students’ acquisition of scientific abilitiesis one of the key aims of this curriculum. When conducting any experiment, students carry out a series of planning, performing and evaluating activities. In order to scaffold novices during these tasks and, more importantly, to scaffold them in the process of acquirement of experimentation related abilities, we provide them with rubrics that can be applied to all of the laboratory activities.The rubrics, which have been developed and validated by our group, facilitate the task of establishing clear, attainable and meaningful goals and offer students a way of self-monitoring their progress.

3. Rubrics support students in two differentways The aim of our rubrics is not only to facilitate the learning of some scientific concepts, ideas and relationships but, more importantly to teach the process and nature of science through the students’ actual practice of the scientific inquiry. Since we are introducing students to the practices of real science, we need to provide them with the necessary support that will enable them to accomplish unfamiliar, complex tasks and, at the same time, learn from the experience. Our aim is that the rubrics will scaffold learners in the course of their knowledge construction in two different ways: first, allowing novices to complete the task, which without help they would not be able to accomplish (since learners will be working at many times during the lesson on the zone of proximal development) and second, but not less important, promoting transfer, that is helping students to complete successfully similar, or not so similar, tasks in the future. In other words we intend that a cognitive residual persists and may become active in different contexts.

4. During regular lab instruction, students design and conduct their own experiments with the guidance of prompts and questions specially written for each particular lab. They assess their work using also the rubrics. During practicals, students are not provided with those specific prompts thereforethey have to rely for help only on the rubrics. Upon removing the prompts and questions,can students perform equally well with the sole scaffolding of the rubrics? We have analyzed students reports of two different application experiments written under the two conditions (with and without prompts). The students are from three different sections taught by different TAs. The number of students that worked on each of the sections is approximately 22.

5. Task A (with prompts) Determine the net force on a conical pendulum Design two independent experiments to determine the net force exerted on a conical pendulum by other objects as the bob of the pendulum moves in a circle at constant speed. Hints: Let the bob move in a circle of larger diameter, say 1m. You could analyze the motion using concepts from kinematics. Equipment: A heavy bob at the end of a string, a meter stick, a spring scale, a stopwatch. Include in you report for each experiment: a) a complete description of your experimental design with a labeled diagram b) a free-body diagram c) a procedure that you will use to determine the net force d) the physical quantities that you will measure and quantities that you will calculate. e) additional assumptions that you made f) sources of experimental uncertainty and ways to minimize them g) perform each experiment and record the data. Compare the two outcomes and discuss if the difference can be explained by your assumptions or uncertainties. h) briefly describe a real-life situation in which you have encounter things similar to this experiment

6. Task B (without prompts) Part 1: Determine the energy stored in the Hot Wheels launcher The Hot Wheels car launcher has a plastic block that can be pulled back to latch at four different positions. As it is pulled back, it stretches a rubber band –a greater stretch for each of the four latching positions. Your task is to determine the elastic potential energy stored in the launcher in each of these launching positions using the generalized work-energy principle. Equipment: Hot Wheels car, Hot Wheels track, Hot Wheels launcher, meter stick, two-meter stick, ruler, masking tape, timer, scale to measure mass.

7. Task B (without prompts) Part 2: Getting the Hot Wheels car to successfully make a loop-the loop Your task is to determine the least energy launching position so that the car will make it around the loop without loosing contact with the loop –on the FIRST TRY (Do not use a trial and error method). If you use the next lower energy setting, the car should not make it around the loop. You may use the results you obtained from the previous experiment. Equipment: Hot Wheels car, Hot Wheels track, Hot Wheels launcher, meter stick, two-meter stick, ruler, masking tape, timer, scale to measure mass, Hot Wheels loop-the-loop and spin-out.

8. The scientific abilities considered in this study In order to complete satisfactory the tasks given to the students in the two instances, they have to display proficiency in a series of key scientific abilities. For this study, we focused our attention on a selection of abilities that students, as well as scientists, must have when designing and conducting application experiments. The criterion for our selection, in addition to its relevance, have been that this collection of abilities was the one in common needed and requested to accomplish the two tasks proposed to students. The researchers have used for scoring the lab reports the same rubrics that the students utilize for guidance and self-assessment, and the same ones that TAs use for grading the experimental work of the students.

10. How werescored the reports ? Find the magnitude of the potential energy stored in each of the launch positions of the “Hot Wheels Launcher”. Scoring samples taken from students’ reports Car is a point particle... ...we are neglecting friction... ...we designate zero “h” at the beginning of the track. System: Earth, track, launcher, car. SCORE = 2 Calculations are correct... ... friction is negligible... ...measured values are correct... SCORE = 1

11. Students’ performance (All sections) Average score per student per ability Condition With prompts1.83 Without prompts1.75

12. Students’ performance (Section I) Average score per student per ability Condition With prompts2.0 Without prompts1.9

13. Students’ performance (Section II) Average score per student per ability Condition With prompts2.0 Without prompts1.9

14. Students’ performance (Section III) Average score per student per ability Condition With prompts1.44 Without prompts1.42

15. Difference between scores under the two conditions(score of the task with prom – score of the task without prompt)

16. Statistical differences Is there a statistical significant difference between the scores of the students under the first and second conditions? z = [(x 1 /n 1) –( x2 / n 2)]/ [(s 12 / n 1) +( s 22 / n 2 )]1/2 At z = 0.22, z< z0.05 (= 2.101), clearly the difference between the mean scoresis not significant. The difference between the two conditions for each of the sections is as well non significant, since z I = 0.51 , z II = 0.35 and z III = 0.05

17. CONCLUSIONS This study shows that our rubrics might help as a tool for procedural facilitation (the investigative steps are explicitly stated). We have not found a significant difference between the effects of the scaffolding by including prompts and questions in the task, and the sole scaffolding of the rubrics. The rubrics help novices to complete the task, which involves complex and unfamiliar scientific abilities. Additionally, we believe the rubrics also improve the transfer of these abilities. These features make the rubrics a helpful tool to guide students through their learning .