A fifth cluster
Worth reading first: The organ that was taken away · The damage has a period.
When a cut wrecks a stem, two adjacent chains of organs change places, and the size of that exchange has an account. It is one step of the control’s divergence, less about a fifth of the surviving hop’s own angle, and it is right in sign on every row it was fitted over.
The rule’s own file states its weakness plainly. Seventeen rows carry eleven hop values in four clusters, because the hop is nearly constant inside a lag — so a rule fitted on the hop is fitted over four numbers however many rows it has.
Why four is a thin denominator
A correction with one free coefficient fitted over four points is a line through four clusters. The coefficient’s value is 0.188 by least squares and is stated as a fifth rather than fitted, because a third digit would be a claim about four measured hops.
Four points also cannot distinguish a linear rule from several others. What they can do is say the sign is right, and the sign is right on every row — the alternatives, the cut stem’s own divergence step and the surviving family’s step, are wrong by up to 82 and 83 per cent. The rival that comes closest is the control’s divergence step with no correction at all, which is wrong by 11.8 per cent on its worst row.
So the rule was in good shape as a description and untested as a prediction. Those are different things and the difference is what a fifth cluster is for.
Where the fifth came from
A search of the fine end of both branches found one lattice whose cuts keep a lag the census does not: the Lucas branch at a rise of 0.006, on the 7/11 rung, whose offsets 8, 9 and 10 keep a lag of 11.
It was added to the census as one extra row rather than as a replacement for it, so the extended table is the old ten lattices plus one and every existing number is answered from the same cache.
The lattice is one rise below one the census already holds, on the same rung, settling to within a sixth of a degree of its branch angle. Nothing about it is exotic; it had simply never been cut.
What the new hop is
12.78 degrees, and it is the smallest in the table by a third. The four clusters the rule was fitted over sit at 19.5, 22.1, 22.8 and 39.1 degrees in magnitude, with the larger negative hops at 21.5 to 37.3.
That matters more than a fifth point usually does. A point between two existing ones is mostly a restatement; a point a third beyond the near end of a fitted range is where a linear rule and a curved one first come apart.
What the rule predicts there
A fifth of 12.78 is 2.56 degrees, so the rule says the exchange should fall about two and a half degrees short of one step of the control’s divergence.
That is a smaller shortfall than anything in the table, which runs from about 4 to 11 degrees, and it is small enough to be swamped by anything sloppy. If the rule were picking up a constant offset dressed as a proportion, this is where it would show.
What is measured
2.09, 2.09 and 2.07 degrees on the three rows, against a predicted 2.56. As a share of the hop that is 0.164, 0.163 and 0.162 against a stated 0.200 and a fitted 0.188.
So the rule is right in sign, right in order of magnitude, and low by about a fifth of itself. The three coefficients land inside the spread the four old clusters already covered — 0.121 to 0.301 — rather than outside it.
That is a confirmation of the useful kind. It is not that the prediction was exact; it is that a point beyond the fitted range did not need a new rule to describe it.
What it does to the fit
The least-squares coefficient over the whole table moves from 0.188 to 0.184. That is a change in the third digit, on a quantity whose third digit was never claimed.
The spread of per-row coefficients does not move at all: 0.121 to 0.301 before, 0.121 to 0.301 after, because the new rows sit comfortably inside it. So nothing about the rule’s uncertainty changed either.
And to the two other claims
The exchange’s file makes two claims besides the size. The first is its direction: the chain displaced forwards is one residue below the chain displaced backwards, on every row. That was seventeen rows, quoted as one in a hundred and thirty thousand under a coin.
It is now twenty of twenty, which is one in a million under the same coin. The three new rows are the ones that extend it rather than rows that were already there.
Where the exchange sits
The second claim is about location: the back-displaced chain is the hole’s own chain on ten of seventeen rows, against 2.8 expected by chance. It was reported as a tendency and not a law, because seven rows put it elsewhere.
All three new rows put it at the hole, so the tally is now thirteen of twenty. The share barely moves — 59 per cent to 65 — and the claim stays what it was.
Three rows all falling the same way is what three cuts on one lattice would do whether the tendency is real or not, so this is the weakest of the three extensions. It is reported because leaving it out would be choosing which of a file’s claims to re-score.
The denominator, said properly
Three rows arrived and the honest count went from four to five. Not from seventeen to twenty.
The three sizes are 97.25, 97.25 and 97.28 degrees — one number three times, because the offsets differ and the rise, the seed angle and the history below the hole do not. Any arithmetic quantified over rows would be counting the same measurement three times, which is the exact criticism the exchange’s own file makes of its seventeen.
So the correct sentence is: a rule fitted over four hops is now tested against a fifth, and it survives. Everything else is bookkeeping.
What a fifth point can and cannot do
It can break a rule and it did not. It can extend a range and it did — the fitted range now runs from 12.78 to 39.14 degrees rather than from 19.5.
What it cannot do is distinguish the rule from its neighbours. A fifth of the hop, a sixth and a quarter all take the worst row from 11.8 per cent to under 6, and one more point at one more hop does not separate them either. That would take several clusters at hops the ladder does not offer.
Which is a limit of the subject and not of the work
That is worth stating because it is where this thread ends rather than pauses. The hops available are decided by the lags available, the lags are decided by the rungs, and the rungs are what the rule that places organs makes.
Eight rungs across two branches, whose smaller numbers are 1, 2, 3, 3, 4, 5, 7 and 8, and one rung whose larger number can survive. That is the whole supply of hop clusters on this ladder and five of them are now in the table.
Two of the eight are too coarse to wreck at all, so they contribute nothing: nothing behind the front wrecks and at the coarse end the front is short enough that no single removal reaches past it.
Why the new hop being small is the useful part
A shortfall proportional to the hop and a shortfall that is a constant look the same over a narrow range of hops. Over 19.5 to 39.1 degrees — a factor of two — they are distinguishable in principle and not comfortably.
At 12.78 degrees a constant shortfall of about 4 degrees would give a coefficient of 0.31, at the very top of the observed spread; a proportional one gives 0.16, in the middle of it. The measurement is 0.163.
So the new point does discriminate, mildly, in favour of the proportional reading. That is a modest thing to get from one cluster and it is more than the four could give.
The control the extension keeps
Every number the old table reported is unchanged, because the extended census is the old list of lattices with one appended and both are answered from the same cache.
That is the discipline the slot table followed when it went from six lattices to twenty-four. A comparison between a table and a longer table is worth nothing if the two are also two implementations, and the way to guarantee they are not is to make the shorter one a subset of the longer.
What the three rows look like up close
All three are balanced pairs: two adjacent chains displaced in opposite directions by the same amount to within a twentieth. That is what makes them usable — the exchange is only defined on a row with a balanced pair in it.
Their chains are 10 and 0 out of eleven, so the forward-displaced chain is one residue below the backward-displaced one, and the backward-displaced one is the hole’s own. That is the pattern every other row in the table has.
A balanced pair is what a chain slipped by one place would produce, and the alternative — a swap — would give a displacement of nothing in the quantity that measures the slip. That test was made on the seventeen and the three new rows agree with it.
And what the other three cuts at that lattice do
The same lattice wrecks at three more offsets, and those keep a lag of 7 rather than 11. None of them is a balanced pair.
So they do not enter the exchange table at all. They go instead to the set the exchange sets aside, where they turn out to be an out-of-sample test of a different rule entirely — one that had been right thirteen times out of thirteen and is wrong on one of them.
One search, two threads
That is worth a sentence on its own because it was not planned. The search was run to find a lag outside the census’s four and it returned a lattice with six wrecked cuts on it: three that answer the question asked, and three that test something else.
Nobody designed the second half. It is the ordinary return on measuring a whole object rather than the part of it a question needs, and it is the reason the census cuts every offset rather than the ones expected to wreck.
What would break the rule
It is worth naming, since a rule that cannot be broken is not being tested. A sixth cluster at a hop of, say, 60 degrees with a shortfall of 4 would put the coefficient at 0.07, outside the observed spread, and the proportional reading would be in trouble.
No such hop exists on this ladder. The largest is 39.1 degrees at a lag of 4, and larger hops need coarser lattices, where a single removal wrecks nothing and there is no exchange to measure.
So the rule is as tested as this subject allows
Five clusters spanning 12.8 to 39.1 degrees, a factor of three, with a coefficient that stays inside 0.12 to 0.30 across all of them and a fit that moves by 0.004 when the fifth arrives.
That is the state of it, and it is worth saying that this is the ceiling rather than a stage. The next test would need a lattice this ladder does not carry.
The prediction that could not be tested
There were two predictions and only one of them had somewhere to be tested. The other was for a golden lattice at a lag of 11, where the exchange was expected to fall about six degrees short of one divergence step.
No golden lattice on this ladder keeps a lag of 11 or 13. At every golden rise on a rung the surviving family ranks second or worse by hop length, and below the finest rung the stem stops settling onto its branch at all. So that prediction is not unconfirmed; it has no object.
The six degrees would not have transferred anyway. It was arithmetic on a golden hop, and the lattice that does keep 11 has a different divergence and therefore a different hop — which is why the rule transfers and the number does not.
A number and the rule it came from
That distinction is worth keeping. A prediction usually arrives as a number, and the number is the rule evaluated at conditions the predictor had in mind.
When the conditions turn out not to exist, the number is dead and the rule may be perfectly alive. Reading the dead number as a dead rule is the mistake available here, and the way to avoid it is to write down which part of a prediction is the rule before looking.
What it cost
Twenty rises cut at every offset, about eight minutes of stems, and a census extended by one lattice, which is another two. Ten minutes to test a rule that has been in the collection since the exchange was first measured.
That is cheap enough to be worth saying out loud, because the alternative was leaving a fitted coefficient unexamined on the grounds that examining it looked like work. The expensive part was deciding where to look, and that was arithmetic on which rungs carry an eleven.
What is left open
Two things, and both are small. The rise at which the surviving family changes on the 7/11 rung is located to within a sixth of the rung, because the search stepped from 0.0070 to 0.0060 in one move; nine rises would place it.
And whether the whole lower quarter of that rung keeps 11, which would make the fifth cluster several rises rather than one. Neither would change the rule’s score and both would make the one case a little less lonely.
What a reader should carry
That a rule fitted over four numbers was tested against a fifth from outside its range, and came back right in sign and low by a fifth of itself — inside the spread its own four already had.
And that the fifth is one lattice and one hop, three rows deep, so the denominator went from four to five rather than from seventeen to twenty. Reporting it the other way would have been the same mistake the rule’s own file was written to avoid.
What the picture at the top shows
Five marks, one per surviving lag, placed by the lag and by the angle of the hop that lag keeps. The shaded band is the range of hops the correction was fitted over.
Four of the marks are inside it. The fifth — the lag of 11 — sits at 12.78 degrees, outside the band at its near end, and the number above it says the table holds three rows there. That is what a test looks like as opposed to a restatement.
The one line
The exchange’s correction was fitted over four hop clusters and is now tested against a fifth at 12.78 degrees, a third smaller than any of them: it predicts a shortfall of 2.56 degrees and the measurement is 2.09, a coefficient of 0.163 inside the 0.121 to 0.301 the four already spanned.
The fit moves from 0.188 to 0.184, the direction claim goes from seventeen rows to twenty, and the honest denominator goes from four to five.
What links here
Computed from the collection, not written here: the essays that point at this one.
Shares its objects with
Essays that name at least two of the same things, and that neither author linked.
- A band with nothing inside it — both name ablation, claim testing, contact family, honest limits, replication
- The wrecking set moves again — both name ablation, claim testing, contact family, honest limits, replication
- A cycle sums to a whole turn — both name claim testing, exchange, falsifiability, honest limits
- Every rise of a band — both name ablation, claim testing, honest limits, sample size
- One offset, two answers — both name ablation, claim testing, falsifiability, honest limits
- One rise per rung is a sample — both name claim testing, falsifiability, honest limits, sample size
Named objects
A flat tag is an object no other essay names yet.
AblationClaim testingContact familyDivergence stepExchangeFalsifiabilityFitted constantHonest limitsHop lengthOut of sampleReplicationSample size