What a twenty-five-question test can and cannot express
A twenty-five question test, the common length for a quiz or a unit test, and the shortest test on which plus and minus grades start to behave sensibly.
Every question on a twenty-five-question paper is worth 4% of the grade, so the only grades that exist are the 25 multiples of that figure. That is coarse enough that 1 of the thirteen plus/minus bands — C+ — cannot be hit at all: the score that first clears the floor overshoots straight into the band above.
The practical consequence is that a borderline case on a twenty-five-question test is decided by a single question. Going from 15 correct to 14 moves the grade by4% — the difference between 60% and 56%, or between a D- and an F on a 60% pass mark. 14 out of 25 is the highest score on this test that still fails.
What each letter needs out of 25
| Letter | Starts at | Lowest score out of 25 | Which is |
|---|---|---|---|
| A+ | 97% | 25 out of 25 | 100% |
| A | 93% | 24 out of 25 | 96% |
| A- | 90% | 23 out of 25 | 92% |
| B+ | 87% | 22 out of 25 | 88% |
| B | 83% | 21 out of 25 | 84% |
| B- | 80% | 20 out of 25 | 80% |
| C | 73% | 19 out of 25 | 76% |
| C- | 70% | 18 out of 25 | 72% |
| D+ | 67% | 17 out of 25 | 68% |
| D | 63% | 16 out of 25 | 64% |
| D- | 60% | 15 out of 25 | 60% |
Clearing the 93% A cut-off takes 24 out of 25, which allows exactly one wrong answer; that score actually lands on96%, an A. A pass at 60% takes 15 out of 25, allowing 10 wrong. Those cut-offs are the common US ones and your school's may differ by a point or two — the percentage column is the part that transfers, and the letter grade to GPA page gives the full band table with grade points on the 4.0, 4.3 and 5.0 scales.
Every score out of 25
25 rows, highest first: the score, the percentage it produces, the letter it lands in on a standard plus/minus scale, and how many questions that leaves wrong. Each score links to a page working that grade out in full, including what the next letter up would take and what the same percentage looks like on a test of a different length.