Interpreting a Similarity Report
Turnitin does not check for plagiarism in a piece of work. Instead, we will check a student's work against our database, and if there are instances where a student's writing is similar to, or matches against, one of our sources, we will flag this for you to review. Our database includes billions of web pages: both current and archived content from the internet, a repository of works students have submitted to Turnitin in the past, and a collection of documents, which comprises thousands of periodicals, journals, and publications.
It is perfectly natural for an assignment to match against some of our database. If a student has used quotes and has referenced correctly, there will be instances where we will find a match. The similarity score simply highlights of any problem areas in a student's paper; you can then use this as an investigative tool, in order to determine if the match is or is not acceptable.
Similarity Reports provide a summary of matching or highly similar text found in a submitted paper. When a Similarity Report is available for viewing, a similarity score percentage will be made available. Similarity Reports that have not yet finished generating are represented by a grayed out icon in the Similarity column. Reports that are not available may not have generated yet, or assignment settings may be delaying the generation of the report.
Note: Overwritten or resubmitted papers may not generate a new Similarity Report for a full 24 hours. This delay is automatic and allows resubmissions to correctly generate without matching to the previous draft.
The color of the report icon indicates the similarity score of the paper, based on the amount of matching or similar text that was uncovered. The percentage range is 0% to 100%. The possible similarity ranges are:
Blue: No matching text
Green: One word to 24% matching text
Yellow: 25-49% matching text
Orange: 50-74% matching text
Red: 75-100% matching text
Refining a Similarity Report
To refine your students' similarity scores, consider the following Similarity Report filters:
Exclude small sources (measured by word number or 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).
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.
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.
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.
A 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.
* An instructor can rectify this issue by excluding by word number. In most cases, excluding 5 words should safely exclude a student's name from being highlighted in their Similarity Report.
A student may have used Turnitin to submit drafts of the same paper, meaning their final draft has resulted in a score of 100%.
* As the instructor is likely aware that their student has submitted multiple times, they can rectify this issue by excluding the student's 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.
* Instructors 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.
* 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.
* This issue could have been avoided if quotes and bibliography had been excluded from the Similarity Report.