“At the end of the semester, the total scores for all students will be arranged in numerical order, the score that corresponds to the 99th percentile (S99) will be determined, and then letter grades will be
assigned based on this percentile score as follows:
A: Total Score ≥ 0.90 x S99
B: 0.80 x S99 ≤ Total Score < 0.90 x S99
C: 0.70 x S99 ≤ Total Score < 0.80 x S99
D: 0.60 x S99 ≤ Total Score < 0.70 x S99
F: Total Score < 0.60 x S99 or if you fail to complete 10 of the 12 lab
projects”
This is the explanation the department of chemistry for my college gives. But I don’t understand, so please explain it to me like I’m five.
In: Mathematics
In this grading system everyone’s performance is judged relative to one person’s grade.
The person they choose is *almost* the highest scoring person. They skip the highest few people in case those people did much better than the rest of the class (e.g. because they have a tutor that classmates had no access to). For every 100 people in the class they skip one person at the top of the class when looking for the person to grade everyone against.
A popular next step that many courses would employ next is to ask what number needs to be added to that person’s grade for them to get a 100. This curve takes a similar step but instead asks what number needs to be multiplied by that person’s score to get to 100. For example, if the chosen person got an 88 then we’d choose 1.1363636… as the number, since 88 * 1.363636… = 100.
The grader then multiplies everyone’s raw score by that number and sorts into buckets. If you land in 90-100 then you get an A; 80-90 is a B, and so on.
(Note that the description you posted does the math in a different order, but this is equivalent).
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