In science writing you will naturally get replication of words because of literature cited and sometimes the methods section - for standard procedures there are a limited number of ways to say it. Taking this into account, I would be suspect of student reports that rise above 20% similarity to other works, and certainly those that are over 30% are likely to have plagiarized. As you mention, phrases or sentences of more than 8-10 words that are not part of the methods or literature cited sections were most likely copied from other sources.

Mitch Cruzan

On 2/2/2018 7:02 PM, Jorge A. Santiago-Blay wrote:
Using Turnitin in science classes

Dear Colleagues:

Finally, I have decided to begin using Turnitin in some of my science classes, including environmental sciences. As a beginning user of Turnitin, I have received valuable feedback on some of the technical settings. However, I have not received feedback on what I considered to be areas where the proverbial rubber meets the road (listed below):

1. How long a string of words do you allow to be OK.? I was suggested 8 words (no scientific rationale behind that was provided).

2. What percentage of similarity is considered to be enough to trigger reporting a work to the superiors for "dishonesty" (or whatever it is called in your schools; after checking with the filters, etc.)

3. Any sliding scale for smaller "offenses" re. percentage of similarity

If you have something constructive to communicate pertaining what do you do in your courses or what is the policy at your institution, please, feel free to email me directly: <>

Apologies for potential duplicate emails.



Jorge A. Santiago-Blay, PhD <>

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Mitch Cruzan
Professor of Biology
Portland State University
PO Box 751
Portland, OR 97207 USA

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