This article also applies to iThenticate.
Turnitin is a tool which highlights similarity to other sources.
It does not determine if a paper has been plagiarised - that is the prerogative of the assessor.
The assessor (instructor/supervisor) has to decide if the similar text has been quoted correctly and attributed accurately.
The context is important, and Turnitin does not account for context.
A high Similarity Index could be due to:
- the student having quoted many other works to a significant extent;
- a long bibliography/reference list in that the paper;
- many common phrases in a particular field which cannot be avoided; and/or
- other legitimate reasons.
Another common reason is that Turnitin is comparing a student's submission to his/her previous submission. This particular case is easy to resolve, just exclude the source(s).
- How similar is too similar?
Plagiarism.org article (retrieved on 7 December 2018)
- Effective solutions for mastering the Similarity Report
Turnitin blog post (retrieved on 7 December 2018)
- Interpreting the similarity report
Turnitin Help (retrieved 19 Feb 2020)