What is the maximum similarity (index) percentage commonly allowed in a scientific report? completely understand that the Plagiarism is never allowed, but I am asking in the context of marking "Masters by Coursework" students' research work.
Approximately 15 percent similarity index should be allowed; even if the similarity index crosses that limit during initial stage of report preparation, it can be brought down with cautious efforts.
To maintain genuine originality of work, you always try to sustain zero plagiarism... One can definately maintain zero plagiarism using some parameters for research writing skills and citation method use.
I personally agree with the answers of Dickson Adom and Nihad Mohammed and others, namely that the maximum similarity is 20%.
However, I actually disagree with Surendra T. Kale. There is an evident difference between plagiarism and similarity, and as the question was concerning similariy I therefore disagree with your answer. Of course plagiarism must be avoided by all means necessary. But again, that was not the question.
@Surendra Tryambakrao Kale. It is nearly impossible to have 0% similarity in your text. For example, if you write the following words in your paper: "Using ultra-high performance liquid chromatography tandem mass-spectrometry for measuring ... " . That is an array of almost 10 words long which will inevitably be marked as similar/not original by most the plagiarism checkers. But those words are universally and widely used in the field of analytical sciences. It is absurd and nearly impossible to state those words other wise. Because then you will have something like: "Using liquified chromatography, the tandem version, combined with mass-spectromatry while having a performance that is ultra-high for ... ". If you actually write that, other scientists will think that you are crazy.