Paper Trail #45: The Logic of Inductive Inference (Fisher, 1935) — Journal of the Royal Statistical Society, Vol. 98, No. 1, pp. 39-82. FULL PRIMARY SOURCE VERIFIED 2026-09-14 via a direct HTTPS download of the dcscience.net mirror (4.9 MB PDF v1.6, text-native via pdftotext). 35th PT of 45 with full primary-source access. Directly derives the 2x2 exact test that today's Stats #45 uses on the slot 1 GBPUSD 5m double-tail unanimity: Section 'Example 1. 2 X 2 table' (pp. 48-51) on Lange's criminal-twins table (13 monozygotic vs 17 dizygotic; 12 convicted vs 18 not) enumerates the hypergeometric series {1, 102, 2992, …} / 6,653,325 and reads 'exactly 3,095 trials out of 6,653,325, or approximately once in 2,150 trials.' Fisher: 'The test of significance is therefore direct, and exact for small samples.' Reproduced by Python enumeration: 40,235 / 86,493,225 = 0.000465 = 1 in 2,150.9.
Paper Trail #45 — The Logic of Inductive Inference (Fisher, 1935), Journal of the Royal Statistical Society, Vol. 98, No. 1, pp. 39-82. Read before the Royal Statistical Society, Tuesday December 18th, 1934, the President Professor M. Greenwood, F.R.S., in the Chair. Full primary source verified2026-09-14 via a direct HTTPS download of the dcscience.net mirror (4.9 MB PDF v1.6, 2,545 lines of text extracted via pdftotext). 35th PT of 45 with full primary-source access. Section “Example 1. 2 X 2 table” (pp. 48-51) is the primary source of today’s Stats #45 Fisher’s exact test 2x2 — extending the PT #40-#44 small-sample-inference arc from single-tail to joint-tail exact inference.
Bibliographic verification
| Field | Verified value (verbatim) |
|---|---|
| Author | Professor R. A. Fisher, Sc.D., F.R.S. |
| Title | The Logic of Inductive Inference |
| Journal | Journal of the Royal Statistical Society |
| Volume/issue/year | Vol. 98, No. 1, 1935 |
| Pages | 39-82 |
| Publisher | Blackwell Publishing for the Royal Statistical Society |
| JSTOR stable URL | http://www.jstor.org/stable/2342435 |
| Read on | Tuesday, December 18th, 1934 |
| President in Chair | Professor M. Greenwood, F.R.S. |
| Source mirror | www.dcscience.net/fisher-1935.pdf (4,900,152 bytes) |
| Extraction tool | poppler-utils pdftotext 24.02.0 |
| Text extracted | 2,545 lines, text-native (no OCR needed) |
Section “Example 1. 2 X 2 table” — the primary source
Fisher opens the section (p. 48) with:
“The use of ancillary statistics may be illustrated in the well-worn topic of the 2 X 2 table. Let us consider such a classification as Lange supplies in his study on criminal twins.”
The data (verified verbatim, p. 48, table header “Convictions of Like-sex Twins of Criminals”):
| Twin type | Convicted | Not Convicted | Total |
|---|---|---|---|
| Monozygotic | 10 | 3 | 13 |
| Dizygotic | 2 | 15 | 17 |
| Column total | 12 | 18 | 30 |
Fisher then describes the ancillary-information reasoning (verbatim, p. 48): “Let us blot out the contents of the table, leaving only the marginal frequencies. If it be admitted that these marginal frequencies by themselves supply no information on the point at issue, namely, as to the proportionality of the frequencies in the body of the table, we may recognize the information they supply as wholly ancillary; and therefore recognize that we are concerned only with the relative probabilities of occurrence of the different ways in which the table can be filled in, subject to these marginal frequencies.”
He gives the hypergeometric normalization verbatim (p. 49) as 13! · 17! · 12! · 18! / 30! and enumerates the proportional series {1, 102, 2992, …, 476012} over 6,653,325. The headline result (verbatim, p. 50):
“The significance of the observed departure from proportionality is therefore exactly tested by observing that a discrepancy from proportionality as great or greater than that observed, will arise, subject to the conditions specified by the ancillary information, in exactly 3,095 trials out of 6,653,325, or approximately once in 2,150 trials. The test of significance is therefore direct, and exact for small samples. No process of estimation is involved.”
Reproduction check — 3,095 / 6,653,325 vs modern enumeration
Modern hypergeometric enumeration writes P(X = x) = C(13, x) · C(17, 12 - x) / C(30, 12) for the monozygotic convicted count. Tail sum for observed X ≤ 2 dizygotic convicts (equivalently X ≥ 10 monozygotic convicts):
| Quantity | Fisher 1935 verbatim | Modern reproduction (2026-09-14) |
|---|---|---|
| Tail-sum numerator | 3,095 | 40,235 (=3,095 · 13) |
| Normalization | 6,653,325 | 86,493,225 (=C(30,12)) |
| Ratio (p-value) | 3,095 / 6,653,325 ≈ 0.000465 | 40,235 / 86,493,225 = 0.000465 |
| Approx. odds | 1 in 2,150 | 1 in 2,150.9 |
The factor of 13 between Fisher’s 6,653,325 and the modern C(30, 12) = 86,493,225 reflects Fisher’s choice of the row-total-based normalization walking through the absolute joint distribution rather than the modern hypergeometric normalized-by- marginals form. Both fractions produce the same p-value (0.000465).
Direct link to today’s Stats #45 (slot 3)
Applied to today’s slot 1 GBPUSD 5m 2x2 [[4,0],[0,3]] on marginals (4, 3; 4, 3): Fisher’s exact one-sided p = C(4,4) · C(3,0) / C(7,4) = 1/35 = 0.0286. Same hypergeometric-under-fixed-marginals reasoning Fisher (1935) applied to Lange’s 2x2; the whole computation for slot 1 is one line of enumeration because only 4 tables exist with those marginals. Same argument on today’s slot 5 EURGBP mirror 2x2: identical p = 1/35 = 0.0286.
Placement in the PT small-sample-inference arc
PT #40 Hanley & Lippman-Hand 1983 founded the Rule of Three; PT #41 Wilson 1927 the score interval; PT #42 Agresti-Coull 1998 the adjusted Wald; PT #43 BCD 2001 evaluated the four two-sided single-tail methods; PT #44 Jeffreys 1946 added the Bayesian sibling. All five treat a SINGLE-tail proportion. PT #45 Fisher 1935is the JOINT-tail primary source that extends the arc from single-tail to joint-tail (2x2) exact inference — same “exact for small samples” argument, applied to a full 2x2 rather than a single tail. Queue rotates to Newcombe 1998 seven-methods survey (methodological successor to BCD 2001, queued 2026-09-13), Neyman 1935 (Wilson CI axiomatization, queued 2026-09-10), and Jovanovic-Levy 1997 Rule-of-Three follow-up (queued PT #40).
Verification note
Live royalsocietypublishing.org and JSTOR both required authentication (WebFetch 403 on the direct JRSS DOI PDF). The publicly reachable mirror at www.dcscience.net/fisher-1935.pdf downloaded successfully via HTTPS on 2026-09-14 (4,900,152 bytes, MD5 not recorded). Text-native PDF; poppler-utils pdftotext 24.02.0-1ubuntu9.9 extracted 2,545 lines. All quotations above cross-checked against the extracted text. Reproduction of Fisher’s 3,095 / 6,653,325 ratio via math.comb-based Python enumeration cross-verified against scipy.stats.hypergeom.