College plagiarism checkers are sometimes wrong, according to a study by Texas Tech. While programs are able to locate matching words, phrases or even paragraphs, such matches do not necessarily indicate plagiarism.
In order to detect plagiarism, the original plagiarized text must be in the program's database, according to Texas Tech Today. One of the programs used in the study, Turnitin, returns a potential plagiarism flag for papers when it finds a phrase in eight other articles it retrieves through a Google search. Turnitin is more likely to flag papers using common phrases such as "a recent study by" or "global warming" than those papers that do not use these phrases.