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Helping students learn to design experiments in an large-enrollment introductory laboratory class

Helping students learn to design experiments in an large-enrollment introductory laboratory class. Sahana Murthy, Eugenia Etkina, Michael Gentile, Aaron Warren, Alan Van Heuvelen Rutgers University, New Jersey http://paer.rutgers.edu/scientificabilities.

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Helping students learn to design experiments in an large-enrollment introductory laboratory class

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  1. Helping students learn to design experiments in an large-enrollment introductory laboratory class Sahana Murthy, Eugenia Etkina, Michael Gentile, Aaron Warren, Alan Van Heuvelen Rutgers University, New Jersey http://paer.rutgers.edu/scientificabilities AAPT National Meeting, Sacramento, August 2004 Supported in part by NSF Grant DUE #0241078

  2. What are design tasks? Students design experiments to • Investigate new phenomena: Observation experiment Example: Design an experiment to devise a rule for the force a magnet exerts on a moving charge. • Test a hypothesis: Testing experiment Example: Your friend says that as current flows through a circuit, it is used up by the elements of the circuit. Design an experiment to test this hypothesis. • Solve a practical problem: Application experiment Example: Design experiments to determine the thickness of a strand of your hair using two independent methods, one of which must involve ideas about diffraction.

  3. Features of design tasks • Part of ISLE cycle: Observation, testing or application experiment • Divergent thinking-- two independent methods to solve problem • Open ended, ill-defined • Need to perform additional experiments or informed estimates to solve task • Task can involve more than one topic in physics • Qualitative and quantitative experiments

  4. Implementation • Large enrollment class -- 450 students • Algebra-based class, health science majors • Lab class accompanies lecture class • 20 lab sections, 6 TAs • TAs not involved in PER activities • Training -- TAs perform mock design tasks • Collaboration with lab coordinator • Design tasks given in 2nd semester of course • One design task per lab • Students perform experiments and write reports in a 3-hour laboratory

  5. Example: MagnetismObservation experiment Design an experiment to devise a rule for the direction of the force a magnet exerts on a moving charge. Equipment: Bar magnet, Cathode Ray Oscilloscope. • Devise and write an outline of your procedure. • Draw a labeled diagram. • List the assumptions that you made. • Perform the experiment and record your observations. Make a table if necessary. • What patterns did you find from your data? • Devise an explanation for the pattern. • Devise a rule for the direction of force that the magnet exerts on the moving charge.

  6. Example: MagnetismTesting experiment Design an experiment to test the rule you developed about the direction of force a magnet exerts on a moving charge. Equipment: Strong horseshoe magnet, power supply, wire. • State the rule that you are going to test. • Devise and write an outline of your procedure to test the rule. • Draw a labeled diagram. • List the assumptions you made. • Make your prediction using the rule and the planned experiment. • Perform the experiments and record the results. Make a table if necessary. • Use hypothetico-deducto reasoning with the arguments and evidence for testing your rule. Is your prediction confirmed? • What is your judgment about the rule?

  7. Example: OpticsApplication experiment Design two independent experiments to determine the width of a strand of your hair. One method must involve ideas of diffraction. Equipment: Laser pointer, meter stick, holder for hair, screen. • Devise and write an outline of the procedure. • Draw a labeled diagram of your experiment. • Write the mathematical procedure you will use. • Write how you will measure the physical quantities you need. • List the assumptions are you making in your design. • Perform the experiment. Record your measurements. • Calculate the thickness based on your procedure and measurements. • What are possible experimental uncertainties? How could you minimize them? Evaluate the effect of the uncertainties on the data. • When finished both experiments, compare the two values for the thickness. What are possible reasons for the difference?

  8. Example: Specific heat Application experiment Design two independent experiments to determine the specific heat of the given rock. Equipment: water, heater, Styrofoam containers, balance, thermometer and timer. • Devise and write an outline of the procedure. • Draw a labeled diagram of your experimental set-up. • Write down the mathematical procedure you will use. • List the assumptions you made. How could they affect your results? • Write down how you will measure the physical quantities you need. • List sources of experimental uncertainty. How will you minimize them? • Perform the experiment and record your measurements. Make a table for your measurements, if necessary. • Calculate the specific heat, based on your procedure and measurements. • After you have done both experiments, compare the two outcomes. What are possible reasons for the difference?

  9. Example: Thermodynamics Application experiment Design an experiment to determine if the power rating of a water heater is reasonable. Equipment: Immersion heater, stopwatch, thermometer, Styrofoam cup and lid. • Devise a procedure and write down an outline. • Draw a clearly labeled diagram. • Write the mathematical procedure you will use. • Write down how you will measure the physical quantities you need. • List the assumptions are you made. How could these affect the result? • Perform the experiment. Record your measurements in an appropriate format. • List sources of experimental uncertainties. How could you minimize them? • Do the necessary calculations. • Make a judgment about whether the power rating is reasonable. • Suggest specific improvements in the experimental design.

  10. Example: Newton’s Laws Application experiment Design at least two independent experiments to determine the coefficient of static friction between your shoe and the carpet. Equipment; Spring scale, ruler, protractor, tape, string, assortment of blocks, hanger, pulley, clamp, force probe. • Devise a procedure and write down an outline. • Draw a clearly labeled diagram. • Draw a free-body diagram for the system with a set of coordinate axes. Use the free-body diagram to devise a mathematical procedure. • List the assumptions you made. How could these affect the result? • List sources of experimental uncertainty? How could you minimize them? • Perform the experiment and record your observations.Make a table if necessary. • Do the calculations. What is the outcome of your experiment? • When finished with both experiments, compare the two values you obtained for the coefficient of static friction. What are possible reasons for the difference?

  11. Development of rubrics • Rubrics based on scientific abilities* • Rubrics match guidelines in experiments • 90% Inter-rater reliability with Rutgers PAER group • Can be used for • Research on development and assessment of scientific abilities • Grading lab reports by teachers • Self-assessment of lab reports by students * Etkina, E., “Developing and assessing scientific abilities in an introductory physics course”, AAPT Announcer, Vol.33, No.4, P.85 (2004).

  12. Research and Findings • 35 students in sample • Randomly selected from 4 sections • Scored student responses from week 3 (initial) and week 10 (final) • Found significant improvement in some scientific abilities Examples of design tasks and scientific ability rubrics are at: http://paer.rutgers.edu:/scientificabilities

  13. Sample student response and scores on scientific abilities Ability Score To design a reliable experiment 3 that solves the problem To choose a productive mathe- -matical procedure for solving 3 an experimental problem To make a judgment about the 2 results of the experiment To communicate the details of an 2 experimental procedure clearly and completely To identify the assumptions made 1 in using the chosen procedure To evaluate specifically how 2 experimental uncertainties may affect the data

  14. Conclusions • Possible to implement and assess open-ended design tasks in large enrollment class • Students’ scientific abilities improved • Assessment rubrics serve as goals for writing new design tasks Further work • Students will be provided rubrics for self-assessment • Controlled experiment to test if guidelines in rubric caused • improvement in students’ abilities • Correlation between students’ scores on abilities and test • scores?

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