Zdeslav Hrepic

1. Zdeslav Hrepic A real-time assessment of students’ mental models of sound propagation Dissertation Defense Kansas State UniversityPhysics Education Research Group Supported by NSF ROLE Grant # REC-0087788

2. Outline • Rationale: Why use in-class, real-time assessment? • Previous research: • Mental models of sound propagation. • Hybrid mental models and their role. • Test construction and validation • Results • Using the test • Further study

3. Real time, in class assessment Uses some form of Class Response System Enables quick collection and immediate analysis of students responses in the classroom.

4. Benefits of class assessment • Engages students. • Facilitates interactive learning and peer instruction (especially in large enrolment classes). • Gives immediate feedback to the teacher. • Enables the teacher to adjust the teachingbeforethe exam rather than after it and according to specific needs of his/her students. • Allows a post lecture detailed analysis.

5. Goal of the study To create a multiple choice test… …that can elicit students’ mental models of sound propagation… …during the lecture… …using a class response system and appropriate software.

6. Mental model definition Mental model is: an internal (mental) representation analogousto the physical worldsituations or processes that it represents and that serves to explain and predict the physical world behavior (Greca & Moreira, 2002) Mental model has: • spatial configuration of identifiable kinds of things • (a few) principles of how system works and • (certain) predictive power (diSessa, 2002) Mental model state: Is defined by student’s consistency (Pure & Mixed)

7. Research questions • Main question: • What is the optimal multiple choice test that can elicit students’ mental models of sound propagation in a real time, during the instruction? • (Some of) Sub questions: • Is model analysis the optimal analytical tool for analysis of students’ responses in this test? • How do we represent data so the display provides a variety of instruction guiding information? • How reliable is the test? • How valid is the test?

8. Starting point in test creation:Identifying mental models of sound propagation Hrepic, Z., Zollman, D., & Rebello, S. (2002). Identifying students' models of sound propagation. Paper presented at the 2002 Physics Education Research Conference, Boise ID.

9. Human characters = Air particles Footballs = Sound entities 4 basic models - mechanisms of propagation

10. 4 basic models - mechanisms of propagation WaveModelScientifically Accepted Model (+) Ear Born Sound Propagating Air Hybrid Models Dependent Entity Independent EntityDominant AlternativeModel

11. Implications of hybrid mental models Implications for analysis of our test • Hybrid models cause overlaps in multiple choice questionnaires – more than one model corresponds to the same choice (E.g.) • Model analysis requires one on one match of model and answer choice Implications for teaching • A student can give a variety of correct answers on standard questions using a hybrid (wrong) model (E.g.)

12. Constructing the test Four steps of test construction and validation: • Pilot testing • Pre-survey testing • Survey testing • Post Survey testing

13. Pilot testing • Did we miss anything in terms of mental models? • Open-ended questionnaire on a large sample • Did we miss anything in terms of productive questions to determine students mental models? • Battery of semi-structured conceptual questions related to sound as a wave phenomena in variety of situations

14. Test Contexts1. Air How does sound propagate in this situation?

15. Test Contexts2. Wall How does sound propagate in this situation?

16. Test Contexts1a, 2a - Vacuum What happens without the medium (air or wall)?

17. Pre-survey testing • 5 option multiple choice test needed • Does our choice selection match students’ “needs”? • Trial with: • None of the above • More than one of the above • Validation through expert reviews • Probing and refining the test through students interviews

18. Survey testing Surveying - to determine: • Stability of results… • …across different institutions at equivalent educational levels • …across different course levels at same institutions • Instructional sensitivity of the test • Correlations between response items • Model distributions at different levels - for future use Interviewing – to determine: • To validate new test version • To inform and make sense of survey findings

19. Test questions - paraphrased • What is the mechanism of sound propagation in the air/wall? • How do particles of the medium vibrate, if at all, while the sound propagates? • How do particles of the medium travel,if at all, while the sound propagates? • What does this motion have to do with sound propagation – cause and effect relationship? • What does this motion have to do with sound propagation – time relationship? • What happens with sound propagation in thevacuum?

20. Displaying the test results • Several representations of students’ state of understanding • Available in real time and in post instruction analysis • Consistency: • Consistent – a student uses one model(Pure model state) • Inconsistent – a student uses more than one model(Mixed model state)

21. Using a particular model Pre Instruction; Calculus based; University; NY Inconsistently Consistently N = 100

22. Using a particular model at least once Pre Instruction; Calculus based; University; NY Inconsistently Consistently N = 100

23. Movements of particles of the medium Pre Instruction; Calculus based; University; NY (+) Random Travel (+) Travel Away From The source Vibration on the Spot N = 100

24. Model states Pre Instruction; Calculus based; University; NY Mixed Any Pure Other Mixed Entity Pure Wave Mixed Ear-Wave N = 100

25. Correctness Pre Instruction; Calculus based; University; NY N = 100

26. Survey participants

27. Survey Results • Results stable? Differences meaningful? • Comparing consistency and correctness • Different levels; Pre- and post-instruction

28. Comparing correctness and consistencyDifferent levels; Pre- and post-instruction

29. Comparing correctness and consistencyDifferent levels; Pre- and post-instruction

30. Comparing model distributionDifferent educational levels

31. Comparing model distribution Grouped models; Different educational levels

32. Comparing model distribution Grouped models; Different educational levels

33. Comparing model distribution Grouped models; Different Educational Levels

34. Comparing model distributionDifferent course levels

35. Comparing differences in model distributionVariability within different educational levels

36. Pre-Post instruction difference *Gain (G) = (post-test) – (pre-test) **Normalized gain (h) = gain / (maximum possible gain) (Hake, 1997).

37. Using a particular model Pre Instruction; Calculus based; University; NY Inconsistently Consistently N = 100

38. Using a particular model Post Instruction; Calculus based; University; NY Inconsistently Consistently N = 95

39. Movements of particles of the medium Pre Instruction; Calculus based; University; NY (+) Random Travel (+) Travel Away From The source Vibration on the Spot N = 100

40. Movements of particles of the medium Post Instruction; Calculus based; University; NY (+) Random Travel (+) Travel Away From The source Vibration on the Spot N = 95

41. Correctness Pre Instruction; Calculus based; University; NY N = 100

42. Correctness Post Instruction; Calculus based; University; NY N = 95

43. Correlation analysis of answer choices

44. Validity interviews • 17 x 4 probes in the interviewed sample. • The invalid display of a model would have occurred in 6 instances • 8.8% of the probes • 3 instances because of 5a (+ another 3 that did not cause invalid probe)

45. Post-Survey Testing Expert review: • To validate post survey version • Few minor items improved • Surveying: • To determine correlations between response items and see if changes made the desired effect. • Problems fixed • Role playing validation: • To validate new test version in an additional way • Perfect score

46. Test Reliability • Reliability pertains to the degree to which a test consistently measures what it is supposed to measure. (Oosterhof, 2001) • Content sampling error • Occasion sampling error • Examiner Error • Scorer Error

47. Reliability addressedContent sampling error • Occurs because students may be more or less lucky with how test items correspond to things they know. • To reduce: Test more content • To measure: Need parallel form • Issues: No parallel form, Context dependence • Reduced by probing a single model multiple times • Addressed by showing meaningful* correlations between the answer choices: • Not neg. if related to same model (pos. and frequently sig.) • Not sig. pos. if related to different models (Except Dependent/Independent entity models - continuum) *Pertain only to secondary and tertiary levels but not to primary

48. Occasion sampling error • Occurs because students can be more or less lucky with respect to time when the test was administered. • To reduce: Test more often • To measure: Need multiple administrations of the same test • Issues: Problematic for instructors and students, Economy • Did not probe time stability • Addressed by showing : • Stable results across institutions at the same level • Meaningful differences between educational levels • Meaningful differences between course levels • Meaningful differences between pre- and post-instruction

49. Examiner error & Scorer error • Examiner erroroccurs because of the differences in examiners. • Not measurable • Was reduced through the standard introduction to the test (verbal and written) • Scorer error occurs if students’ scores depend on who happened to mark their work. • Not an issue - computerized analysis of results. All four of the treats to the reliability well addressed Gives a ground for the statement that the test is a reliable instrument.

50. Validity addressed Test Validity: • The extent to which a test measures what it is supposed to measure and nothing else. (Oosterhof, 2001) • “Validity concerns the appropriateness of inferences and actions that are based on a test’s scores”. (Hanna, 1993, p. 8) • Validity is not an attribute of the test, but “of the interaction of a test with a situation in which the test is used to make decisions”. (Hanna, 1993 p. 382) • Content-related evidence of validity • Criterion-related evidence of validity • Construct-related evidence of validity