1 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 2002Summary The Computerized Homework Assignment Grading System (CHAGS) is a web-based 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. 21. 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 3before plugging in the final values have more than enough time to complete the assignments. 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 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 29The 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
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