Plagiarism threshold?

[Vark]

What is the general threshold for considering a paper plagiarized? If less than that threshold has been plagiarized, how much should the paper be marked down? What does it mean when Turnitin highlights sentences in green?

[downer]

I recommend you talk to your department chair and consult the student handbook or college website about the plagiarism policy.

For questions about turnitin.com, I'm sure they have a help facility and a guide for faculty.

[nescafe]

Yeah. Turnitin doesn't take all the work out of detecting plagiarism. It only highlights material that is replicated elsewhere. You will have to go and confirm that it is indeed lifted from another source manually.

[Aster]

You should not be looking for the plagiarism detectors to give you a silver bullet score.

The score value just tells you how much "identical-looking stuff" got flagged. It will not distinguish "false positive" plagiarisms like references, quotations, graphics, etc... You have to sort all that out yourself.

There is no threshold score from these software packages. You still need to go into each and every paper that's been flagged and examine the flagged content to see if its actually been plagiarized or not. And for most professors, the plagiarized content will be subjectively screened by you to see if it meets your individual "smell test" for academic dishonesty. This varies on a multitude of factors that only you should determine for your specific course. Like how your course is handled for group work or collaborative work, submitting previous work, sharing illustrations or tables, quoted works, etc...

All that said, if you see a 100% match on a submitted paper, somebody is definitely in trouble.

[Caracal]

What is the general threshold for considering a paper plagiarized? If less than that threshold has been plagiarized, how much should the paper be marked down? What does it mean when Turnitin highlights sentences in green?

f you mean some numerical threshold based on Turnitin scores, that wouldn't make any sense. I haven't used Turnitin in a few years, but when I did, I saw lots of papers with high scores just because they quoted extensively, although perhaps that has been fixed. You can also see things flagged that just happen to use similar language or words, but clearly aren't plagiarized because they have nothing to do with the topic of the paper.

There's also the issue of intent and context. If a student quotes directly from a source, but then later directly lifts a few sentences from that source without attribution, that is probably a result of carelessness and I wouldn't consider it to be academic dishonesty. On the other hand if the student's thesis statement was directly lifted from a source that they never mentioned in the paper or included a reference to, that is pretty clearly plagiarism, even if it is just two sentences.

To answer your other question, you have to first decide based on your judgement, not scores, whether the student deliberately committed academic dishonesty. If they did, then you follow the procedures on that which probably involves giving the whole thing a 0 as just a starting point. You only get to the point of grading down if you decide that it isn't plagiarism, but just carelessness. How much would depend on the extent of the problem. A forgotten quotation mark is basically just a typo, if the student has hopelessly mixed up their own language with others that would be a big issue.

[Parasaurolophus]

If it's a citation error--e.g. quotation marks but no citation, or clear paraphrase without citation--then I accept it. But if it's not--e.g. no quotation marks and no citation, or a thesaurus paraphrase with no citation--then a single instance suffices for me.

[spork]

If it looks like a duck, sounds like a duck, and tastes like a duck, then it's a duck until proven otherwise.

[LetsGetCooking]

The percentage match is virtually meaningless. It takes work to determine if a student plagiarized or cheated.

Students have submitted papers with a high percentage match that were not plagiarism, just quoted extensively. If the matches are properly cited, then it is not plagiarism, just over-quoting (Feedback was to balance evidence and discussion better. Evidence should be used as support, not dominate!)

I have received LOW percentage papers that WERE plagiarism and/or cheating. When I investigated, it was clear that the material that did not match was either missed by Turnitin for some reason or that the student had altered the surrounding wording with a thesaurus. The blatant plagiarism and/or cheating was clear despite the low match percentage.

One feature that I use a lot is "exclude sources".

First, each Turnitin match is often to multiple possible sources. I use "exclude sources" to attribute to one source as much as possible. For example, a paper might have a 30% match with 10% each to three sources: Sparknotes, Schmoop, and Cliffsnotes. Upon review, the list for each match includes Sparknotes. So, I "exclude sources" so that all 30% is matched to Sparknotes.

Second, I have the feature that matches student papers turned on since there is a lot of cheating at my school where students hand in papers from other students who took the same class previously. Often, Turnitin returns a student paper from another school as the primary match, but a review of the other possible matches reveal a website, journal article, or book. So, I often exclude student papers from other schools manually so that only web or printed sources remain. (This takes work, so I usually only do it for cases where I suspect plagiarism or cheating, not every paper). I NEVER base decisions about plagiarism on matches that ONLY show a student paper from another school unless I request the paper and receive it from them and see the matches for myself. I have had false positives in the past, so
I don't trust them.

I HATE how Turnitin designates primary matches. It breaks up matches between multiple possible sources when there is clearly one source after the other options are excluded. For example, I recently had a student turn in a paper with a 40% match score. It included a high percentage to Sparknotes and a few other websites, but this assignment prohibits the use of any source but the textbook. However, upon examining the list of possible sources for each match, I found our textbook. It was waaaaaaaaay down the list, but when I excluded all of the other sources, Turnitin showed that the entirety of the 40% match was the course textbook. (I would have known the material was from the textbook, but I checked the originality report before looking at the paper just in case it was a cheater since high percentages like that in this course often mean cheating).

Overall, Turnitin can be a useful tool, but it is not a replacement for the professor's discernment.

[Vark]

A student of mine included two sentences (on different pages) that were taken from outside sources but not designated as quotes. How much should I reduce the grade by?

[Caracal]

A student of mine included two sentences (on different pages) that were taken from outside sources but not designated as quotes. How much should I reduce the grade by?

Well, what kind of outside sources are we talking about? Are these source that the student cited elsewhere in the paper?

[Vark]

One source was cited in the same paragraph and one source was not.

[Caracal]

One source was cited in the same paragraph and one source was not.

If they cited the source in the same paragraph, that is probably just a careless mistake. For the other sentence I'd want to know more. They didn't cite it anywhere in the paper? What sort of sentence was it, can you be totally sure this comes from that source and there isn't some other explanation?

[Vark]

I am completely sure that both sentences came from the sources. In the first case, the source is cited and then two other quotes from the source are placed in quotation marks. In the second case, no source is cited in the paragraph.

[Caracal]

I am completely sure that both sentences came from the sources. In the first case, the source is cited and then two other quotes from the source are placed in quotation marks. In the second case, no source is cited in the paragraph.

Ok, but the second source doesn't show up anywhere else in the paper at all?

[Vark]

The second source does not show up in the paper, although a different type of quote from the same source (placed within quotation marks yet with no source indicated) appears in the same paragraph. In this case, a quote from an interviewee is placed in quotation marks, but a sentence-long description by the writer of the piece is not placed in quotation marks.