To refine your students' similarity scores, consider the following Similarity Report filters:
Exclude small sources (measured by word number of percentage)
You can exclude sources in the source list that are below the threshold set by you. For example, if the threshold is set at 3%, any 1% or 2% match would be removed from the current report mode's source list (Match Overview or All Sources).
Exclude quotes and bibliography
Quotes and bibliography items are widely reused and generally fail to demonstrate original writing. You may wish to exclude quotes, bibliographies, and items of a similar nature from influencing your students' similarity scores.
Exclude full sources
The source exclusion feature is generally used when a paper has been submitted more than once to Turnitin (possibly as draft submissions). Sources may also be excluded when an instructor agrees that students use a certain source for their writing.
Generate a new Similarity Report
If you believe an item may have been added to the Turnitin database since a Similarity Report was last generated (this could be a website, journal article, or even another student’s paper), you can generate a new report to receive an up-to-date score.
Similarity Scoring Examples
Your student may have submitted a paper to Turnitin in the past. If they had their name on that submission, it is entirely possible that, if you have not excluded small matches, their name is highlighted in their Similarity Report.
Tip: You may opt to exclude by word number. In most cases, excluding 5 words should safely exclude a student's name from being highlighted in their Similarity Report.
Your student may have used Turnitin to submit drafts of the same paper, meaning their final draft has resulted in a score of 100%.
Tip : As you're aware that your student has submitted multiple times, you can rectify this issue by excluding their previous submissions from the Similarity Report.
A student has copied and pasted a chunk of text into their paper, due to a lack of knowledge on the topic they are covering. Their similarity score is 20%. In comparison, another student who has a firm basis of knowledge for the same assignment and knows enough to gather information from several sources to quote and reference correctly has a similarity score of 22%. Both students will be shown to have matches against our database. However, one of these students copied directly from a website, whereas the other provided properly sourced quotes.
Tip: You can opt to exclude quotes from the Similarity Report to lower similarity scores where applicable.
A student has managed to acquire a copy of another student's paper. They submit this paper to Turnitin on 15th October and receive a similarity score of 25%. The student who originally wrote the paper submits it to Turnitin a week later, receiving a 100% similarity score.
Tip: In this case, regenerating the Similarity Report of the student who plagiarized will immediately identify collusion allowing you to follow institutional regulation.
A student has submitted a qualitative study to Turnitin, including a significant number of quotes and an extensive bibliography, as required for the topic of the paper. The student's similarity score is 53%; this exceeds the acceptable score set by their institution.
Tip: This issue could have been avoided if quotes and bibliography had been excluded from the Similarity Report.
At this time of year, we hear a lot of chatter from students via Twitter (follow us: @turnitin) saying, "turnitin says my essay was 23% plagiarized," or "just submitted my paper to turnitin... 4% plagiarism is good right?," or "my Turnitin plagiarism percentage is only 18%."
There is a very distinct difference between what Turnitin flags as matching text (aka: similarity index) and plagiarism. Turnitin will highlight ANY matching material in a paper—even if it is properly quoted and cited. Just because it appears as unoriginal does not mean it is plagiarized; it just means that the material matches something in the Turnitin databases.
We leave it to the instructors to look at a paper and the originality report to make the determination of whether or not something is plagiarism, and to what extent—intentional plagiarism, unintentional plagiarism, improper/lack of citation, or mere coincidence. Best practices from instructors suggest that Turnitin OriginalityCheck be used as a teaching tool to address citation and academic honesty, not only as a punitive tool.
There is also a helpful video for instructors on how to view the OriginalityCheck Report and goes over many of the OriginalityCheck features. There is a similar video tutorial for students on how to view their OriginalityCheck feedback as well.