tfs nzip 2011
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The Concept of Force and the Mechanics Curriculum
Terry ScottAndrew Gray
Daniel Schumayer
StatisticianNot a Statistician
Minion
The Force Concept Inventory
• Concept Inventory rather than a “test”.
• 30 multichoice questions.• Very good distractors:– Guessing success very low– Reliability unusually high– Pre and post test design seems to work
well
The Force Concept Inventory
FCI - Uses
• Standard uses:– Evaluate development of conceptual
understanding.– Evaluate teaching methods.
• Our research:– Search for conceptual coherence.– Understand associations in student mind.– Inform teaching method.– Suggest future research.
Data Collection
• FCI delivered online (Blackboard)• PHSI191 – Large Health Science
service course.• 2000 student responses collected
over two years, 2008 and 2009.• Not obligatory.• Data checked for disengaged
responses– 50 response sets removed.
Data Analysis
• Exploratory Factor Analysis– Construct correlation matrix (using tetrachoric
correlations)– Find eigenvalues/eigenvectors.
• What does this mean?– Factors = latent traits/concepts – Factors represent student understanding of force.
• How do students group questions, which questions are about the same thing?
• How does this compare with the way experts group questions?
Interpretation
• 5 factors found in the analysis.• These factors are not orthogonal – Correlations between factors – useful
information
• Clear that there is conceptual coherence in the data.
• Better score = greater conceptual coherence?– No evidence, not enough data
The Factors
• Factor 1 – Identification of forces.• Factor 2 – Newton’s first law, linear
and curved paths.• Factor 3 – Newton’s second law +
necessary concepts (acceleration, velocity).
• Factor 4 – Newton’s first law with zero net force.
• Factor 5 – Newton’s third law.
Factor 1 – Identification of Forces.
Factor 2 – Newton’s First
Factor 3 – Newton’s Second
Factor 4 – Newton’s First Again
Third Law/First Law conflation – Qu.16
Kinematics?
• Authors of the FCI included a number of questions solely about kinematics concepts.
• We find no factor containing only kinematics questions.
• Kinematics questions are distributed “where they are needed” in factors about force laws.
Item Response Analysis - Preliminary
• Preliminary results• Show third law questions significantly
higher difficulty that other questions• Marginal analysis– Assess student ability, predict the
questions they will get right.– Anomalous numbers of students get 3rd
law questions right but 1st and 2nd law questions wrong.
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