1PhysicsDepartmentTexas A&MUniversityC.H.A.G.S.Computerized Homework Assignment GradingSystemPHYSICS 218 'Mechanics'WEB-BASED HOMEWORKA.Mershin, D.Toback, J.WalkerMay 2002SummaryThe Computerized Homework Assignment Grading System (CHAGS) is a web-based interface that collects and automatically grades homework assignments. Currentlythe system is implemented for Physics 218, which uses Giancoli's University Physicsbook. This system has been developed based on the AMES math quiz software alreadyadopted by Physics 218. The system does not require installation of any special softwareand gives students immediate feedback on their performance. It removes the need forgraders as well as the problems associated with an imperfect grading process. To use thesystem, all a professor has to do is pass out a handout to class (see page 12), anddownload their students' homework grades from the physics web site as necessary.To see an example of CHAGS (homework assignment of chapter 2), log in withyour Physics Web userid/pass to:http://www.physics.tamu.edu/QUIZ/view.html/CHAG_CH2In this example, the correct answer is highlighted. When students use the system, theyhave to pick the right answer from the five (shuffled) possibilities.21. MotivationThe motivation behind developing an entirely automated system which collectsand grades Physics 218 homework comes from our observation that students whodiligently 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 timerequirements for graders, TAs and professors. By requiring that students submit theirhomework weekly (for credit) we hope to increase the overall class standard and alsoprevent students falling behind and cramming for exams. We note that this is animprovement over the current system in which the HW is purely optional.2. Two goals and how they are achievedI. Eliminate the need for homework gradersCHAGS uses software previously developed for the AMES math quizzes(http://www.physics.tamu.edu/QUIZ/). The homework assignments from chapters 1-14 ofGiancoli have been coded into the system and the collection and grading is done entirelyautomatically. There is no need for homework graders and the only action necessary bythe 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 numbersA widespread disability of Physics 218 students is "symbol fear." Students like touse numbers and calculators wherever possible, and frequently lose track of the physicsinvolved in their calculations. To combat this, it is necessary to insist that final answers toappropriate problems be given in formula form before any numbers are substituted.However, one must also teach what numbers are 'reasonable' for various physicalquantities such as mass of a person, or acceleration of a car. CHAGS is formulated in away that requires the students to address both issues and our design is such that studentsare encouraged to use their calculators only once they have the correct formula.The system works on the assumption that students have completed theirhomework in the traditional way (on paper) and have their final solutions and theirtextbook with them when they log in to the system. They are then presented with a set ofproblems virtually identical to the ones in their assignment, but with one number orparameter changed and five multiple choice answers. This means that all they have to dois substitute the new number into the formula for their final result and choose the correctanswer. This (eventually) demonstrates to the students that re-calculating everythingnumerically is a time consuming and undesirable way of handling physics problems. Thisalso prevents students from simply copying the answers from the various solutionmanuals available. Since the final answers are in fact numerical, students still get a tasteof what values are reasonable for various quantities. Our experience tells us that in the beginning, students will try to do the problemsduring the 40 minutes allotted to them and fail. They will then complain that they do nothave enough time. We also know that students who have their answer in symbol notation3before plugging in the final values have more than enough time to complete theassignments. 43. 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 ofcommon 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'sassignment have been chosen. Each web-homework is between 10 and 20 questions longand each question has five possible replies. There is a time limit of 40 minutes and once astudent submits his answers, the system immediately grades them and gives feedbackmarking correct and incorrect answers. If an answer is incorrect, the right one is notshown, 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 homeworkassignment, which gives them an opportunity to re-think any problems that they mayhave answered incorrectly.The system asks the student what the solution would be if one number orparameter were modified. This way the students cannot simply copy the numbers fromthe solution manuals. This also means that they are forced to have their final solutions insymbol form so they can easily substitute the changed parameter.The example shown below is based on Giancoli's Vol.1, (3rd Edition), Problem 29Chapter 2 page 40. 5(Example) Giancoli Chapter 2 Problem 29The original problem reads:29. A car accelerates from 12m/s to 21 m/s in 6.0s. What wasits acceleration? How far did it travel in this time? Assumeconstant 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 =
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