Strength of Materials (SOM) Concept Inventory

Jim Morgan, Texas A&M University

Jim Richardson, University of Alabama

Presentation Outline

• Background

• Preliminary Assessment Results

• Example Questions from Inventory

Purpose

Purpose: Assess students’ mastery of SOM concepts

Motivated by personal experience

SOM’s Place in the Curriculum

• Calculus Physics Statics SOM

• SOM concepts are new to students

• May preclude “pre-testing”

• SOM concepts are essential to follow-on

courses

SOM Concepts

• Shear & Bending Moment Distributions

• Stress & Strain– Axial & Torsional on Rods– Axial, Shear & Bending on Beams

• Axial Buckling

• Pressure Vessels

• Failure of Ductile & Brittle Materials

Development Process

• Met with developer of FCI

• Shared with professors

• Interviewed students

• Pyschometric assessment (on students who have already taken SOM)

• Modify concept inventory

• Beta version available by Jan. 2002to do

Item Difficulty(Percent who got the item correct)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Q1 Q3 Q5 Q7 Q9 Q11 Q13 Q15 Q17 Q19 Q21 Q23

Question Number

Dif

fic

ult

y In

de

x

Questions are very difficult

Questions are very easy

DiscriminationHow well do questions discriminate between high and low scorers?

(Interpret as percent more high scorers than low scorers who got the question correct)

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Q1 Q3 Q5 Q7 Q9 Q11 Q13 Q15 Q17 Q19 Q21 Q23

Question Number

Dis

cri

min

ati

on

Ind

ex

Poor discrimination

Correlation of Inventory to SOM Grade

0

5

10

15

20

25

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Grade in SOM Course

Sc

ore

on

Inv

en

tory

R = .343R-square = .118F (28,1) = 3.595 = .069

26 %

42 %

32 % correct answer

48 %

correct answer

40 % 12 %

correct answer

88 %

2 %

10%

Conclusion

• Good start on a SOM concept inventory

• Psychometrics show it needs more work

• We plan to modify the inventory this Fall

• Release the beta version in Jan. 2002