Discussion section: Rough calculation to explain unexpected results Unexpected results were attained in a simulation that point to a possible problem with the dataset. While writing about this in the discussion section, I'd like to elaborate on my explanation for this by presenting a simple calculation that reinforces my interpretation. Is it allowed to do this in a discussion section or should I lay the foundation for this in the method section and then include it in the results?
Generally yes. The purpose of a discussion section is to interpret your results, both in light of what was previously known (hopefully described in the introduction), and with new supporting arguments or hypotheses. A calculation (possibly short or rough) is a good way of providing a supporting argument, and it's quite common to see one in the discussion section of a scientific paper. However, theses are often subject to local rules, some of which may be silly, so make sure to check your institution's style or thesis guide, or check with your advisor whether they have any preferences.