Please see pp. 42-45 in the Guide to Writing a Senior Thesis in Government.
However, in brief the process is such: Two readers assess the thesis (in the case of joint theses, at least one reader in each department reads the thesis). If the two readers’ grades differ by more than one full grade, the thesis is sent to a third reader. In the former case, the grades are simply averaged; if a third read is required, the median grade is weighted at 50% and the outliers at 25%. If a graduating senior is a potential candidate for highest honors, he or she may be asked to sit for an oral exam as well. If that is the case, the grade received in the oral exam is also averaged in. Next, the Faculty Concentration Committee meets to set a provisional cutoff for each level of honors (this differs from year to year). Once this is done, the thesis grades and concentration GPAs are examined in a faculty meeting open to all thesis advisors and faculty members. There, the final honors determination cutoffs are drawn. Once this is done, the English honors have been determined for the Department. However, it is ultimately the University that awards Latin honors on the diploma, so the Department forwards our honors recommendations to University Hall, where the cutoffs for Latin honors are decided separately, with an eye to their distribution across the entire graduating class.