Physics Department
Texas A&M University
C.H.A.G.S
.
Computerized Homework Assignment
Grading System
PHYSICS 218 'Mechanics'
WEB-BASED HOMEWORK
A.Mershin, D.Toback, J.Walker
May 2002
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Summary
The Computerized Homework Assignment Grading System (CHAGS) is a webbased interface that collects and automatically grades homework assignments. Currently
the system is implemented for Physics 218, which uses Giancoli's University Physics
book. This system has been developed based on the AMES math quiz software already
adopted by Physics 218. The system does not require installation of any special software
and gives students immediate feedback on their performance. It removes the need for
graders as well as the problems associated with an imperfect grading process. To use the
system, all a professor has to do is pass out a handout to class (see page 12), and
download their students' homework grades from the physics web site as necessary.
To see an example of CHAGS (homework assignment of chapter 2), log in with
your Physics Web userid/pass to:
http://www.physics.tamu.edu/QUIZ/view.html/CHAG_CH2
In this example, the correct answer is highlighted. When students use the system, they
have to pick the right answer from the five (shuffled) possibilities.
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1. Motivation
The motivation behind developing an entirely automated system which collects
and grades Physics 218 homework comes from our observation that students who
diligently do their homework perform better on the exams and the rest of the course.
However, collecting and grading homework in the traditional way presents heavy time
requirements for graders, TAs and professors. By requiring that students submit their
homework weekly (for credit) we hope to increase the overall class standard and also
prevent students falling behind and cramming for exams. We note that this is an
improvement over the current system in which the HW is purely optional.
2. Two goals and how they are achieved
I.
Eliminate the need for homework graders
CHAGS uses software previously developed for the AMES math quizzes
(http://www.physics.tamu.edu/QUIZ/). The homework assignments from chapters 1-14
of Giancoli have been coded into the system and the collection and grading is done
entirely automatically. There is no need for homework graders and the only action
necessary by the professor is to download the final homework grades at the end of the
semester (available in text, HTML or Excel format).
II.
Teach both symbols and numbers
A widespread disability of Physics 218 students is "symbol fear." Students like to
use numbers and calculators wherever possible, and frequently lose track of the physics
involved in their calculations. To combat this, it is necessary to insist that final answers to
appropriate problems be given in formula form before any numbers are substituted.
However, one must also teach what numbers are 'reasonable' for various physical
quantities such as mass of a person, or acceleration of a car. CHAGS is formulated in a
way that requires the students to address both issues and our design is such that students
are encouraged to use their calculators only once they have the correct formula.
The system works on the assumption that students have completed their
homework in the traditional way (on paper) and have their final solutions and their
textbook with them when they log in to the system. They are then presented with a set of
problems virtually identical to the ones in their assignment, but with one number or
parameter changed and five multiple choice answers. This means that all they have to do
is substitute the new number into the formula for their final result and choose the correct
answer. This (eventually) demonstrates to the students that re-calculating everything
numerically is a time consuming and undesirable way of handling physics problems. This
also prevents students from simply copying the answers from the various solution
manuals available. Since the final answers are in fact numerical, students still get a taste
of what values are reasonable for various quantities.
Our experience tells us that in the beginning, students will try to do the problems
during the 40 minutes allotted to them and fail. They will then complain that they do not
have enough time. We also know that students who have their answer in symbol notation
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before plugging in the final values have more than enough time to complete the
assignments.
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3. The homework assignments:
The homework interface is user-friendly, with a pleasant layout with color
images. The questions are multiple-choice with push-buttons and they follow the
arrangement of common computerized tests such as the SAT and the GRE.
All questions are based on the homework assignments from Giancoli's book.
Subsets of the most appropriate (usually the hardest) questions of each chapter's
assignment have been chosen. Each web-homework is between 10 and 20 questions long
and each question has five possible replies. There is a time limit of 40 minutes and once a
student submits his answers, the system immediately grades them and gives feedback
marking correct and incorrect answers. If an answer is incorrect, the right one is not
shown, so the student must re-attempt the particular problem. If a question is left blank,
there is no feedback. The students are allowed three chances to submit each homework
assignment, which gives them an opportunity to re-think any problems that they may
have answered incorrectly.
The system asks the student what the solution would be if one number or
parameter were modified. This way the students cannot simply copy the numbers from
the solution manuals. This also means that they are forced to have their final solutions in
symbol form so they can easily substitute the changed parameter.
The example shown below is based on Giancoli's Vol.1, (3rd Edition), Problem 29
Chapter 2 page 40.
(Example) Giancoli Chapter 2 Problem 29
The original problem reads:
29. A car accelerates from 12m/s to 21 m/s in 6.0s. What was
its acceleration? How far did it travel in this time? Assume
constant acceleration.
The correct answer is: a=1.5m/s2 and x=99m
The web problem reads:
Giancoli Ch.2 Prob. 29
(0229) If you change the time to 3.0s then the answer becomes:
a a = 3.0 m/s2, distance traveled = 49.5m
b a = 1.5 m/ s2, distance traveled = 99m
c a = 4.50 m/s2, distance traveled = 297m
d a = 0.75m/s2, distance traveled = 49.5m
e It is absolutely impossible to solve this question with the new value of the time!
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4. Submitting the homework
Students taking Physics 218 register with the system following the directions
presented in the "CHAGS Handout" (cf. page 12). This begins on the web where students
encounter the login screen with directions for setting up a password
(http://www.physics.tamu.edu/QUIZ/login.html).
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As soon as the students register with their name, section number, email, phone
number and student ID, they are ready to begin submitting homework. All information is
communicated via a secure connection. Note that the system gives options for
username/password recovery in case the students forget theirs.
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Below is a sample homework-opening screen.
Once students reach the end of the assignment they can submit it for grading or
ask for all their answers to be reset. Note that they can change their answers at any time
before they hit the "Submit" button.
After students are satisfied with their answers and they hit the "Submit" button,
they are shown their score and are given feedback on their performance on the individual
questions. If students are unhappy with their score they can simply click on the "Try
Again" button and submit again, presumably after they have reviewed the incorrect
answers. There is a limit of 3 submissions per homework and only the best score is
counted.
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Note that correct and wrong answers are clearly marked and questions left
unanswered are not marked at all.
.
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4. Professor instructions and student handout
HOW TO USE C.H.A.G.S. IN YOUR CLASS
 Pass out the "CHAGS directions" handout (see next page)
to your students along with your syllabus on the first day of
class. You may wish to familiarize yourself with its contents
as the students are instructed to start submitting their
homework in the second week of class.
 Check your students' performance and download their
grades on the web using the following URL:
http://www.physics.tamu.edu/QUIZ/topten.html
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CHAGS directions for Physics 218 students
Homework assignments are an integral part of Physics 218 course and they must be submitted
via computer weekly. Experience has shown that students that do all of their homework in a timely
manner, in addition to earning the homework points, do well in other aspects of Physics 218 such as
exams and recitation quizzes.
The Computerized Homework Assignment Grading System (CHAGS) is based on the
mathematics evaluation quizzes (AMES) and is designed to reward you for doing your homework
diligently and to give you immediate feedback on how well you're doing.
This system works on the assumption that you have completed all of your homework
problems before you attempt to submit your answers. You should bring your textbook, a calculator
and your solutions with the final answer highlighted and in formula form (if possible) to the
computer that you will use to access CHAGS. Once you log in, you will need to select the week's
homework assignment. The problems are virtually the same as those in the book but one of the
numbers or parameters has been changed (this is done to prevent you from succumbing to the
temptation of copying the solution from the back of the book and also to show the value of obtaining
final solutions in formula form so substitutions are easy to do).
For instance, if the book Ch.1, Prob.1 asks "What is the time taken if the distance traveled is 35miles
and the speed is 70mph?" your solution should read:
t=x/v
=>
t = 35miles/70mph = 0.5hours
You then should CHECK your answer with the back of the book (for odd numbered questions) or the
web solutions for even numbered questions:
(http://physics218.physics.tamu.edu/answer/giancoli/).
Once you're done with the entire assignment, you can log into CHAGS (see below) and you will see
something like:
Ch.1 Prob.1 "Suppose the speed is 60mph, what is the new time?"
Since you already have the correct formula above, all you need to do is substitute 60mph for v and
pick the correct solution from the five available answers.
To register with the system (not necessary if you already have an AMES userid/pass):
 Go to URL http://www.physics.tamu.edu/QUIZ/login.html and follow the on-screen
instructions to set up your AMES/CHAGS account. You should have your Physics 218
section number and student ID number handy (NB: only the last five digits of your ID or
SSN will be recorded).
Submitting the homework:
 Once you are registered with the system, you can begin submitting homework from any
campus computer with Internet access. Just go to:
http://www.physics.tamu.edu/QUIZ/select.html
and choose the correct chapter. Each time you submit, CHAGS will immediately show
you which questions you answered correctly and which not. There is a 40-minute time
limit for each submission (which is ample -but only if you have your answers in formula
form) and you are allowed 3 submissions per homework with only the highest-scoring
one counting. For off-campus computers you must either have a TAMUnet modem
connection or have a VPN (Virtual Private Network) client running (e.g. if you have a
cable modem or DSL connection). For more information about VPN and TAMUnet,
please refer to the CIS support staff: (979) 845-8300.
 You can check your homework scores by referring to the bottom of the feedback screen.
If you have any questions regarding CHAGS you can email Prof. David Toback
(toback@physics.tamu.edu). For specific problems regarding registration/lost passwords etc. please
email Joel Walker (jwalker@physics.tamu.edu). For questions/comments regarding individual quiz
problems contact Andreas Mershin (mershin@physics.tamu.edu).
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5. Student Feedback
Prof. Toback's, spring '02 Physics 218 class used CHAGS for all their homework
assignments. We surveyed the students asking them about their experience with this
system. The questionnaire and the results obtained are summarized below (grading
4=best, 0=worst). 61 students returned completed questionnaires.
COMPUTERIZED HOMEWORK ASSIGNEMENT GRADING SYSTEM (CHAGS)
In an attempt to improve your performance in PHYS218 by motivating you to do homework questions, we have
implemented a web-based homework assignment grading system. This semester was our first attempt and we will use your answers to
improve this system for future generations of Aggies. This questionnaire will be used purely for CHAGS evaluation purposes so
please answer anonymously and honesty. Your comments (on the other side of this sheet) are greatly appreciated and the more
specific the comment the easier it will be for us to fix the problem.
1)
2)
3)
Approximately how many of the 12 homework assignments did you submit on the web?
Most or all
about 9
about 6
about 3
()
()
()
()
4pts
3pts
2pts
1pts
On average, how many times did you submit each assignment?
1
2
3
0
()
()
()
()
What was your average score (approximately)?
90-100%
80-89
70-79
()
()
()
60-69
()
none
()
0pts
below 60
()
4) The computer interface was easy to use (including registration/passwords, pushbuttons, feedback screen)
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
()
()
()
()
()
5) The wording of the questions was clear i.e. it was easily understood what was asked
Strongly agree
Agree
Neutral
Disagree
()
()
()
()
Strongly disagree
()
6) The questions were relevant to the material in the book
Strongly agree
Agree
Neutral
()
()
()
Disagree
()
Strongly disagree
()
7) The questions were relevant to the material in the exams
Strongly agree
Agree
Neutral
()
()
()
Disagree
()
Strongly disagree
()
8) You felt the system motivated you to do the homework diligently
Strongly agree
Agree
Neutral
()
()
()
Disagree
()
Strongly disagree
()
9)
You felt that submitting the homework assignment on the web and receiving immediate feedback improved your
understanding of the material
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
()
()
()
()
()
10) You felt that the grading of the assignments was fair and any inconsistencies were resolved
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
()
()
()
()
()
11) Any queries, bug reports etc. were promptly and correctly dealt with (leave blank if you didn’t have any queries)
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
()
()
()
()
()
Please use the other side of this sheet for your comments, -
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Average response VS question number
4.00
Average response (max=4, min =0)
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Series1
1
2
3
4
5
6
7
8
9
10
11
3.68
2.34
3.63
3.19
2.92
3.36
2.86
2.56
2.52
2.88
2.87
3.6
4
question number,
average response
Number of students VS average response
25
20
15
10
5
0
0.2
0.6
1
1.4
1.8
2.2
2.6
3.2
More
6. Interpretation of the data and Conclusions
The Computerized Homework Assignment Grading System eliminates the need for
homework graders and motivates students to do their homework. It also sets a clearer and
higher standard of understanding of the material as the norm for Physics 218. CHAGS is
very easy to incorporate into the class syllabus. It is a clear improvement over the current
system that has the homework component of the course as optional with no mechanism
for feedback. Finally, according to the data from our survey, students' reaction was
overall positive (average response 3.5 out of 4.0).
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7. Acknowledgments
We wish to thank Prof. Kenefick who was very helpful in TA-ship arrangements
needed for the development of this system. We also wish to thank the Physics
Department for its support and the students from Prof. Toback's spring '02 class for
identifying bugs and giving valuable feedback that allowed fine-tuning of the system.
8. Relevant web addresses and contact information:
Prof. David Toback has been the driving and coordinating force behind the
CHAGS project since its inception in the Spring of 2002, providing direction and
securing funding. Joel Walker has developed the software and Andreas Mershin wrote
the problems.

For more information, comments/suggestions regarding any aspect of CHAGS
please contact Prof. David Toback (toback@physics.tamu.edu)

For specific information, comments/suggestions etc. regarding the software
contact Joel Walker (jwalker@physics.tamu.edu)

For specific information, comments/suggestions etc. regarding CHAGS content or
this brochure please contact Andreas Mershin (mershin@physics.tamu.edu)

To take a sample homework, first create an AMES/CHAGS userid/pass at:
http://www.physics.tamu.edu/QUIZ/login.html by choosing "sample" instead of
section number and then logon to CHAGS at
http://www.physics.tamu.edu/QUIZ/view.html/CHAG_CH2
(Change CHAC_CHX to see various chapters (1-14 available) and bring the
Physics 218 textbook with you.)
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