Findings · Evaluation integrity
Two language-model judges scoring the same 45 GSM8K answers disagreed with the ground truth in opposite directions: one systematically too strict, the other too lenient.
Evidence
The two judges agree with each other most of the time on this corpus, raw agreement 0.911 and 0.956 against the ground truth. What that scalar hides is the direction of the errors. gemma3-as-judge fails four correct answers (false fail); llama3-as-judge passes two wrong answers (false pass). A single accuracy figure near nine in ten reads as “mostly right” and conceals that the two judges are wrong in opposite ways, which is the difference between a strict grader and a lenient one. A distinction that matters when a judge decides whether a model passed.
Grade before the judges
Grade these five real answers yourself first, passed or failed, then meet the
two graders. Source: evaltrust @ 18e999a5, data/real/ (real judge runs on GSM8K). Nothing leaves your browser.
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Q1. Janet’s ducks lay 16 eggs per day. She eats three for breakfast every morning and bakes muffins for her friends every day with four. She sells the remainder at the farmers' market daily for $2 per fresh duck egg. How much in dollars does she make every day at the farmers' market?
Eggs laid: 16 Eggs eaten: 3 Eggs for muffins: 4 Eggs sold: 16 - 3 - 4 = 9 Price per egg: $2 Daily earnings: 9 * 2 = $18 The answer is 18.Graders: llama3 (language-model judge): passed substring (string matcher): passedTruth: the answer was correct. -
Q2. On the first day of school, Ava sees that her friends Cole and Xavier have both grown a lot over the summer. Xavier was 4 feet tall and grew 3 inches. Cole was 50 inches tall and grew 2 inches over the summer. What is the difference between Cole and Xavier’s height now?
Xavier's growth: 3 inches. Xavier's initial height: 4 feet = 4 * 12 = 48 inches. Xavier's current height: 48 + 3 = 51 inches. Cole's growth: 2 inches. Cole's initial height: 50 inches. Cole's current height: 50 + 2 = 52 inches. Difference: 52 - 51 = 1 inch. The answer is 1.Graders: llama3 (language-model judge): passed substring (string matcher): passedTruth: the answer was correct. -
Q3. John cuts down an 80-foot tree. He can make logs out of 80% of it. He cuts it into 4-foot logs. From each of those logs, he cuts 5 planks. He then sells each plank for $1.2. How much does he make?
1. Usable wood: 80 feet * 0.80 = 64 feet 2. Number of logs: 64 feet / 4 feet/log = 16 logs 3. Number of planks: 16 logs * 5 planks/log = 80 planks 4. Total earnings: 80 planks * $1.2/plank = $96 The answer is 96.Graders: llama3 (language-model judge): passed substring (string matcher): passedTruth: the answer was correct. -
Q4. Cedar Falls Middle School has students in grades 4 – 7 and each year they are challenged to earn as many Accelerated Reader points as they can. The 10 students in each grade with the most points get to try an escape room set up by the teachers. Only 8 students can try the escape room at a time. They have 45 minutes to try and escape. If every group uses their full 45 minutes, how long will it take for everyone to try the escape room?
There are 4 grades (4, 5, 6, 7) with 10 students each, so there are 4 * 10 = 40 students total. Since only 8 students can try the escape room at a time, there are 40 / 8 = 5 groups. Each group takes 45 minutes. Total time = 5 groups * 45 minutes/group = 225 minutes. The answer is 225.Graders: llama3 (language-model judge): passed substring (string matcher): passedTruth: the answer was correct. -
Q5. Billy is peeling and cutting potatoes in preparation for making potato salad for his big family reunion barbecue. It's a big event, so he has 60 potatoes to get through. The potatoes are roughly the same size, so it takes about the same amount of time to peel and cut each one. It takes Billy about a minute and a half to peel a potato, but only about 5 seconds to cut it up. How long will it take Billy to finish prepping the potatoes?
Let's break it down: * Peeling each potato takes 1.5 minutes (90 seconds) * Cutting each potato takes 5 seconds * Total time per potato is: 90 seconds + 5 seconds = 95 seconds = 1 minute and 35 seconds * Billy has 60 potatoes to prepare To find the total time, multiply the time per potato by the number of potatoes: 1 minute and 35 seconds x 60 = ? The answer is 87 minutes.Graders: llama3 (language-model judge): passed substring (string matcher): passedTruth: the answer was wrong.
The two graders agree with each other on every one of these. How reliable would you call them?
Sample. 45 real GSM8K trajectories (trial 0 of each model-by-task cell). gemma3 disagreed on 4 of 45, all too strict; llama3 on 2 of 45, all too lenient.
Boundary
That either judge is reliable, or that the direction generalises beyond this corpus. The sample is small; the per-answer correctness labels are assistant-adjudicated, not human; and two of the three judges also generated answers in the set, so self-preference is uncorrected.
Independent reproduction. None known. Replication is invited.
Reproduction
python scripts/build_report.py && python scripts/recompute.py && pytest -q - Toolchain
- Python >=3.11, numpy >=1.24, scipy >=1.10; judge models are local Ollama llama3, gemma3, hermes3 at temperature 0
- Expected output
- writeup/report.md rebuilt; digest byte-identical to 62bb20c4a8bcd334a6ccd2d04398e6bff29943f76916ad4c5a92c51a723dc10a
- Claim stated at
- repowazdogz-droid/evaltrust · writeup/report.md:40,44; writeup/WRITEUP.md:171-173
- Verified at
- repowazdogz-droid/evaltrust@18e999a5 (2026-07-20)
This pass. Confirmed by source read at 18e999a5 (the committed digest and report were verified present); the recompute pipeline was not re-run this pass.
Artifact: repowazdogz-droid/evaltrust