READ-ONLY. Nothing built or fixed; the four challengers untouched.
41% OF THE REPORTED GAP WAS A MEASUREMENT ARTIFACT. p_win is P(graded
side); proj_p_over_line is P(over); 31.4% of settled rows are UNDER-graded,
so comparing them raw measures the ladder backwards on a third of the
sample. Matched + direction-aligned (n=437): 0.252 vs champion 0.352, not
0.108 vs 0.331. The PRODUCT is not making this mistake -- I checked;
projectionChallenger normalises both to the over basis deliberately. The
error was in the measurement.
THE LOSS IS CONCENTRATED. hits (n=245, res 0.060) and total_bases (n=49,
res 0.009) are 67% of rows and carry essentially no signal. Everything else
is fine or better: walks 0.519 vs champion 0.544, runs mean 0.345 vs 0.392,
and on DOUBLES the ladder's mean BEATS the champion's (0.207 vs -0.062).
IT IS THE MEAN, NOT THE SHAPE. On the two failing families the mean itself
carries no signal (0.052, -0.019) against the champion's 0.158 and 0.085.
Where the mean is good the probability is good -- shape follows mean.
A HYPOTHESIS I TESTED AND DISPROVED: prediction compression. I expected
P(>=1 hit) to sit in a narrow band and fail to rank. It does not -- spread
ratio 0.94 overall, 0.80 for hits, 0.94 for total_bases. The ladder has
comparable spread; it is spread in a direction uncorrelated with outcomes.
Recorded because it was a plausible story the data refused.
PRIORS AND PLUMBING CLEAN. proj_factors carries form_rate,
combined_multiplier and breakdown on every row; proj_point 100% populated
with sane centres (hits 0.830 vs line 0.578). Not the environment-style
silent-null failure.
NAMED CAUSE (structural, flagged as hypothesis not finding): the count
model mismatches those two stats. total_bases is a WEIGHTED SUM (1B..HR =
1..4), so an NB treats one home run as four events and mis-states variance
-- and TB has the worst result in the table. hits is BOUNDED BY AT-BATS and
mostly traded at 0.5, so almost everything rides on P(0), the region where
the wrong family hurts most. walks/runs/doubles ARE genuine low-rate counts
and are exactly the ones that work.
FIX BRANCH: targeted per-stat fix for hits and total_bases. THIS REMOVES
THE MLB SIMILARITY BUILD FROM THE CRITICAL PATH -- that branch assumed a
GLOBAL mean weakness, and the mean is fine or better on three of six stat
families. Similarity may be worth building later, on evidence, not on this.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QJs13VsyiSKYQP6rj3NNmc
