How to Compare Two Documents for Plagiarism

Plagiarism may have serious academic consequences, but F's on assignments or expulsion from school often aren't enough to keep students from doing it. While search engines, essay writing websites and a simple copy and paste function make plagiarism easier than ever, it's still possible for you to spot its warning signs. Comparing the writing style and formatting of two documents makes it easier to detect acts of academic dishonesty as you grade.

Inconsistencies in voice and writing style are a major clue that you may be grading a plagiarized essay. Most instructors have their students do enough short writing assignments, homework and essays that they get to know their individual voices fairly well. As a result, sudden changes in vocabulary level, grammar and sentence structure can provide clues to academic dishonesty. Compare the student essay with the suspected source of plagiarism by reading through both papers and taking note of instances where the author's voice is similar to the student's paper.

Comparing the two papers' use of research is another key plagiarism detection tool. Students often cite the source of the plagiarism as a reference at least one or two times in the paper, according to the University of Michigan Law Library. If a source shows up frequently in the essay, it might be worth investigating the original document for similarities in style and content. You can also examine the two papers' citations for use of mixed academic styles, such as MLA and APA, or a style other than the one required for the assignment.

Detecting plagiarism can often be as simple as comparing the ways the two documents look. Use of the same font or abrupt changes to different fonts can indicate that the student paper copied and pasted sections of the original paper. The essay may also contain formatting that is peculiar to the original website or document, such as hyperlinks, headers with different page numbers or student names or changes in the text's color. Comparing the student paper to the original for these formatting changes can help confirm a case of plagiarism.

Ultimately, the most direct sign of plagiarism is the presence of the same words and sentences in both essays. The use of as few as three consecutive words from another work might be enough to constitute plagiarism, according to the University of New Mexico Graduate Resource Center. Even if the exact original wording isn't present, other major similarities can indicate academic dishonesty. Words from the original document that have been replaced with synonyms, reordered or added or deleted in the student essay can indicate that the content has been strategically altered.