Tips on understanding a Turnitin Report
Turnitin will find most things1 and 2 that are present both on the internet and a student submission, but it must always be an academic decision about whether that constitutes plagiarism. We in the Learning Technology Group can give advice on that interpretation, but ultimately it is for the department to decide what they are looking at.
Please note that the Learning Technology Group strongly recommend that if you start to feel that there might have been any plagiarism as you start to go through the work of a class that you must submit the work from all the students on that assignment to Turnitin, because of the possibility of collusion in plagiarism, or because more students than you may initially realise are having trouble understanding what is expected of them when they write an essay.
If you have access to an electronic version of one student essay or dissertation then you have access to work submitted from all students, and the batch submission facility makes checking everyone's work easy. You therefore might as well check everyone's work, and Learning Technology Group recommend that if you use Turnitin at all, that you always use it for every piece of work in any tested assignment. This is really important if you are going to check student work properly; if you have questions about the importance of doing this, then please do contact the Learning Technology Group.
To continue with the analysis though; here is how the software works:
The first thing is that the software detects matches with material on the internet, journals and other student essays. It does not detect plagiarism, which is a judgement on what the matches represent. There is therefore no percentage that constitutes plagiarism, and the average percentage matching will vary from course to course. The person checking the student work should, when using Turnitin be looking for unusually high percentage scores compared to others on the course (another good reason for checking everyone's work), and checking those with unusually high scores first.
A quick scan of an essay with a noticably high score will reveal in seconds whether the student has deliberately tried to pretend the work of others is his, or is just because a student has forgotten to put the quotes in, as shown in the example from the last section below.
The above article is of course nothing like a real essay, but one feature that emulate the sort of mistake that students make when referencing is shown where attributation is done by placing the name of the author at the end of a piece of text, but because the quote isn't delimited by quote marks, Turnitin doesn't pick it up. Another similar thing for students to do is to work a sentence or two of an authority in the field into his/her essay, altering a few words to make it fit, and starting with something like: "As J.K.Galbraith said.... ". Again, no attempt to conceal the source, but Turnitin won't like it.
On the other hand, if Turnitin finds matches of paragraphs with no attempt to attribute them to the source, then the student may not understand the concept of an original essay.
Occasionally, the student may understand what is expected of them, but may have tried to plagiarise. Often, a tell-tail sign of this is that the student will have altered a few words at the start and end of a paragraph to make it fit in with other bits in the essay. The overall effect is rather ugly and most readers will notice that something's wrong. In our experience, in most case, an essay with plagiarism in it can be detected within a few seconds of reading it because the author's "voice" keeps changing within the essay as the student dips into one nicked bit of text after another. In many cases, Turnitin is used when the script being marked sounds odd to the reader. This happens with longer essays and dissertations. With short pieces of work, set in the 1st and 2nd years, the subjects are too generic and it's sometimes more difficult to say for sure that work has been copied, and then a scan of all work by Turnitin can highlight problems with essays so that students can be detected early on, before they humiliate themselves by getting caught when they don't write final year work correctly.
A video by Turnitin that goes through the reporting facility very well, and shows extra facilities can be reached by this link: http://www.turnitin.com/static/support_video_gallery_instructor_viewingor.html
For advice on where to look for information about what constitutes plagiarism, and where students can get help with referencing, look at 11: Advising Students.
1 Turnitin will find most of the material placed on the internet. There are one or two exceptions. These include material that has only just been placed there - the company that runs Turnitin doesn't reveal its algorithm, but we've found material put on-line in the past week isn't picked up. Another exception are said to be essay banks - these are said to detect the type of detailed rapid network scan that search engines like the one Turnitin use and hide things from them. We also believe that it is weak at picking up stuff that is contained within Wikis.
2 Turnitin will find most of the matches with the internet - but exactly what it finds can vary from day to day. A colleague in another department submitted an essay that was suspect for another colleague without a Turnitin account. The essay must have been submitted to an assignment set up so the essay was not recorded in the Turnitin essay database. LTG set up a Turnitin account for the colleague with the essay, and the essay was submitted again to the new account to show this colleague how Turnitin works. The first upload scored 51%; the second scored 44%. The uploads were separated by two days. Turnitin must have changed their algorithm over the two days. Turnitin support at Lancaster were not aware of any notification of this change, and so it seems possible that the Turnitin company can sometimes make changes without notification.
This highlights the fact that Turnitin is _not_ a precise tool. It can be used to provide evidence - after all, if it finds a link to a piece of text in a published journal that's identical to unacknowledged text in the student's essay, that's not good for the student. But don't rely on it like it's the definitive rating of whether a student used material from elsewhere and didn't acknowledge that, because Turnitin is just not that good.