Remember that Turnitin is only a text matching tool; staff marking assignments are the detectors of plagiarism. The overall similarity percentage is not in itself an indicator of plagiarism - it depends what the match consists of.
Turnitin has both:
- False positives (where matches are highlighted to text that is not problematic, eg cover sheets, institutional addresses, reference lists, commonly used references, templates, quotations, appropriately cited tables, standard academic phrases, etc.), and
- False negatives (where no matches are found, but markers may find similarity to texts by using other software or Google, or checking source texts themselves).
High scores do not necessarily indicate plagiarism; reasons could include lists of appendices or given tables, and extensive use of quotations.
Low scores do not necessarily indicate absence of plagiarism, as Turnitin does not find all plagiarism, and essay writing companies are known to produce texts with 0% match. Low scores may also indicate poor or little research or use of sources, so do not set out with the aim of keeping Turnitin scores low - set out with the aim to write effectively with sources.
More important than the overall similarity are the highest ranked sources in the breakdown of matches. If there are high individual matches, this may indicate plagiarism, or if correctly cited and formatted, may indicate over-reliance on sources, although there may still be understandable reasons for high matches.
Oxford Brookes University adheres to these principles as outlined in the policy.