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Re: [vox] code sleuths needed - cheating suspected
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Re: [vox] code sleuths needed - cheating suspected

I was never a grader, but I did at times act as a consultant in our CS labs,
so I may not be that much of an expert here.  My opinion is that these are
copies of each other.  Now whether they're direct copies, or just the result
of two people helping each other?  My opinion is they are direct copies.

First of all, there are many similarities in style.  Secondly, the changes
between the two files are cosmetic, and look dilberate.  I took a  look
using sdiff and it looked weird.  It looked like lines were added, and lines
were changed, but only in a cosmetic fashion.  It looked like whoever did
this wanted a diff to show everything different.  If both students were new
at C programming, then it would explain a bunch, but judging from the
programs, they do not look to be that new at this.  Things like commenting,
I mean why use two different styles with the same comments, it doesn't make
much sense to me, unless you're trying to make them seem different.  I may
be wrong on this, but I suspect they're copies of each other changed in a
cosmetic fashion to fool the grader.  Again, Don is right, you have to
consider the situation, and compare both students past work to this and see
if a better conclusion can be reached.  However speaking of my own expertise
of reading and writing more C than I can remember(I have been coding C for
10 years now) and plaugurizing, er cut/paste(Hey, that block looks neat, I
can yank and put and adapt it to fix my current issue) another countless
number of lines, it looks to me like they're direct copies that have been
adapted.  If I had to quantify how sure I was, Id say Im 70% sure.

----- Original Message -----
From: "Peter Jay Salzman" <p@dirac.org>
To: <vox@lists.lugod.org>
Sent: Wednesday, November 13, 2002 11:29 AM
Subject: Re: [vox] code sleuths needed - cheating suspected

> begin donw@examen.com <donw@examen.com>
> > On Wed, Nov 13, 2002 at 11:06:58AM -0800, Peter Jay Salzman wrote:
> > > dear all,
> > >
> > > i suspect a student has copied a homework assignment from another
> > > student.  call them "student 1" and "student 2".
> > >
> > > [snip]
> > >
> > > i won't mention the reasons why i think the two codes are similar.
> > > instead, i'll let other people analyze it themselves.  i first
> > > copying because as i read through student 1's code, i kept saying to
> > > myself "this is my own coding style".  then i remembered that i wrote
> > > part of student 2's code who came to me for help with the program.
> > > two of them are friends and work together.
> > >
> > > i'm curious to know what people think.
> >
> > Hmmm...while I'm hardly an expert, a few points come up:
> >   - Student 1's initial code example is very poorly commented (almost no
> >     comments).  Comments in the code turned in by student 1 for the
> >     assignment are almost idential to those in student 2's code.
> >
> >   - Variable names are identical.
> >
> >   - Indent style is inconsistent; however, this looks like a first-year
> >     class, so that can be attributed to students playing around and
> >     a coding style they are happy with.
> >
> >   - The only thing that really bugs me is that the equation bits in the
> >     middle (inside of the for-loop) are set up in an identical fashion.
> >
> > A conclusion?  Not really much of one; it could be a copy, but then
> > the similarities can be accounted for because the two likely work
> > and help each other out.  In my CS classes, when I was stuck on a
> > I'd look at some sample code, and certain things (variable names,
> > algorithms) would often end up the same in whatever I was writing, just
> > because they were in cache at the time.
> >
> > I'd make a judgement call as a professor.  How many assignments have
> > turned in?  Is this code uncharacteristic of Student 1's work; e.g.,
> > he usually turn in broken code, but this one works?  Do you have any
> > reasons to suspect cheating?
> hi don,
> yeah.  quite a few things, but i still want to hear what other people
> have to say.   but i'll give one reason that people may not catch:
> the line:
>    int    N = (b - a) / h + 2;
> is just wrong.  i wrote this line in a rush while 30 students were
> asking for my attention.  the "+ 2" is just a hack.  it's wrong.  it's
> there because i stupidly relied on integer division.   it works for
> b=10, a=0 but doesn't work for, for example, b=10.5 a=0.
> another thing that caught my eye:
>    if ( (fp = fopen("plotpoints.dat", "w")) == NULL)
> inconsistent spacing of the outer parenthesis shows up in both codes.
> there's a lot of other things, but i'd like to hear other comments
> before i give my list.
> pete
> --
> Fingerprint: B9F1 6CF3 47C4 7CD8 D33E 70A9 A3B9 1945 67EA 951D
> _______________________________________________
> vox mailing list
> vox@lists.lugod.org
> http://lists.lugod.org/mailman/listinfo/vox

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