Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Random Number



Hello, phys-l:

This was a few days ago and maybe the problem has been solved, but here is what I do, if anybody is interested, regarding the problem of students copying solutions to numerical HW/exam problems:

I currently teach quantitative chemical analysis/equilibrium and the course has lots of numerical calculations.

Years ago, my students would pester me for "practice exams" before the actual exams and I ended up writing essentially two exams (but I didn't grade the practice exams.) Now I give my students a "take-out exam" a week before the actual, in-class exam; both are graded and weighed equally.  The questions are not necessarily similar, but I can obviously ask different types of questions on the take-out, requiring students to look up data, etc.  Students tend to agree this helps them study/get ready for the in-class exam.  By the way, we (NMU) are a "lap-top" campus, but I really don't think it is practical to have students logon, download an exam, and work it out in 50 minutes.  But they all can do spreadsheet calculations/modeling at their schedule w/o waiting in line at the computer room.

When I used to give "take-home" exams, I would make students sign off that they did not discuss the exam with others, but, as you imagine, some students merely signed, but did not honor the code.

Now, I simply assign a "random" number to each student at the beginning of each semester (but you could change them periodically.)  (Note: I don't use SS #'s and I don't post grades according to random #; we are prohibited from that at NMU.)  Everybody knows everybody else's number and when I work out an example in class, students follow it up with their number: multiply (divide) your number by a constant to get the starting mass/volume/concentration/temperature/etc.; makes for some neat things to plot at the end of class, when you have 20 students, each calculating something slightly different (in physics it would be final position, velocity, voltage, etc.)  For the take-out exams, I really don't care if students work together or not: each student must submit his/her paper, worked out with his/her number.  Of course, I have to code the solutions into a spreadsheet, but that really isn't difficult: copying the formulas for an array of random numbers.  One thing to remember is to not make the spread too large, or some students could get a much easier/tougher problem than others.  For my current 20 students, I use 110-130 for the random numbers, but could use, say, 1000-1020, but then only a 2% range results and some problems result in essentially (3-4 sig digits) the same answer.

Sometimes I don't want different numbers for everybody and I assign students, say, #1-5 and tell them group 1 use 1.23 for the mass, group 2 use 1.26, etc.  Sometimes they assemble into groups and are required to put solutions on the board.

I have not used it yet, but WebCT has the feature of customizing exams, i.e., automatically generating different numerical starting values, but I'm old fashioned and still pass out paper copies.

 Joseph E. Sabol, Ph.D.
 Department of Chemistry
 Northern Michigan University
 1401 Presque Isle Avenue
 Marquette, Michigan 49855
 phone: 906.227.2919
 fax: 906.227.1066
 e-mail: jsabol@nmu.edu

At 04:00 AM 3/12/2002, you wrote:
At 05:24 PM 3/10/02 -0500, you wrote:

I will try it and see.  I have been give a class of freshman
science and all they want to do is copy the answers from
someone else.  I thought if I could quickly generate
several versions or the worksheet it would help to
discourage the behavior.  I could and have gone back and
just rwtyped numbers, but it would be nice to press a
button and have all the numbers automatically print.

We have been using WebAssign for student homework and it gives each student
different numbers to work with and discourages the copying you and many of
us have struggled to avoid.  It works very well and students like using the
system.