What every word on this site actually means.

In one sentence: treating a decision as something with stated inputs, an explicit probability, a success test written in advance and a recorded outcome, so the quality of the reasoning can be judged separately from the luck of the result.

Most tools help you organise a decision. Decision intelligence goes further: it commits to a number before the answer is known, and then goes back afterwards to check whether that number was any good. It is the checking that makes it intelligence rather than presentation. LEXUN is not financial, legal or medical advice, and it never decides for you — it makes your own reasoning explicit enough to be wrong in public.

In one sentence: a range such as 55–65% rather than a single number, where the width of the range is the honest amount of uncertainty.

A model that tells you "61.4%" is claiming a precision it does not have. LEXUN rounds every probability to 5-point steps and then widens the band by two things: the standard error of the simulation itself, and how much of your input was measured fact rather than assumption. A wide band is not the model being unhelpful. It is the model declining to lie about how much it knows.

In one sentence: how often this outcome happens across the broad class of similar situations, before anything specific to you is considered.

The reference class is the group your situation belongs to; the base rate is what usually happens to that group. Starting from the base rate and adjusting is far more reliable than reasoning from your own case alone, because your own case always feels exceptional and usually is not. When LEXUN cannot find a defensible reference class for a question, that is one of the reasons it will decline to answer.

In one sentence: running the same model thousands of times with randomly drawn inputs to see the spread of possible futures — but from a fixed starting seed, so the same inputs always produce exactly the same answer.

Monte-Carlo simulation is old, public and unremarkable; anyone can implement it. The seed is the part that matters here. Because the randomness is deterministic, a LEXUN result is not a one-off performance you have to take on trust — you can re-run it and get the identical output, byte for byte. Reproduce a result in your browser to see this happen.

In one sentence: a rule that stops the model running at all when there is not enough real information to run it responsibly.

The gates are specific: the model refuses when core inputs are marked unknown, and it refuses when every single input is an assumption rather than a measured fact. This is deliberately inconvenient. A product that always produces an answer is a product that produces answers it has not earned, and the commercial pressure runs entirely in that direction — which is why the refusal is built into the engine rather than left to judgement.

In one sentence: a real, valid output of the engine, not an error message.

When a gate trips, LEXUN says it cannot answer and tells you which input would change that. Treating "I don't know" as a legitimate result rather than a failure is the difference between a forecasting tool and a confidence generator.

In one sentence: the test for whether a forecast came true, written down before the outcome is known and never edited afterwards.

Without this, scoring is meaningless: anyone can be right in retrospect by quietly redefining what they meant. Freezing the criterion at prediction time is what makes a later score a fact about the forecast rather than a story about the forecaster. Every entry in the forecast register carries one.

In one sentence: whether the things you called 70% likely actually happen about 70% of the time.

Calibration is not the same as being right a lot. A forecaster who says 90% about everything and is right 90% of the time is well calibrated; one who says 99% and is right 90% of the time is overconfident, even though both were right equally often. Calibration can only be measured from outcomes that have actually resolved, which is why LEXUN's published record is currently an honest zero — see the Accuracy Centre, which prints that zero rather than hiding it.

In one sentence: the average of the squared difference between what you said would happen and what did, where 0 is perfect and 1 is as wrong as it is possible to be.

If you forecast 0.8 and the thing happens, the outcome counts as 1 and that forecast scores (0.8 − 1)² = 0.04. If it does not happen, it scores (0.8 − 0)² = 0.64. Averaging that over many forecasts gives the Brier score. The number worth remembering is 0.25: that is what you get by saying "50%" to everything forever, so any scoring system that cannot beat 0.25 has told you nothing at all.

In one sentence: a good decision can have a bad outcome, and a bad decision can have a good one, so the two have to be scored separately.

If you take a well-reasoned 80% bet and land in the 20%, you were unlucky, not wrong; if you take a reckless 5% bet and it lands, you were lucky, not clever. Judging decisions purely by how they turned out teaches you the wrong lesson in both cases. When you resolve a decision in LEXUN it asks you to separate the reasoning, the execution and the result, because the fix for each is different.

In one sentence: something has moved enough since you decided that the decision deserves revisiting.

A decision is made against a set of assumptions on a particular day. Those assumptions expire quietly, and the usual failure mode is not noticing. LEXUN records what the decision assumed, so it can flag when an assumption you relied on no longer holds instead of leaving that to memory.

In one sentence: a SHA-256 hash taken over the exact bytes of a result, so anyone can later prove the result has not been altered.

Each result is sealed with its hash, and the record of results is hash-chained — every entry commits to the one before it, so a changed entry in the middle breaks every hash after it. You do not have to trust us for this: you can check a receipt yourself without an account, and the check runs in your own browser.

In one sentence: a passcode you choose that encrypts your saved decisions on your own device, which we never receive and cannot recover.

The passcode is stretched into an encryption key using PBKDF2-HMAC-SHA256 at 600,000 iterations, and the record is encrypted with AES-256-GCM. The consequence is worth stating bluntly: because the key never leaves your device, losing the passcode means losing the saved record, and there is no reset link we could honestly offer you.

In one sentence: your decision data is stored in your browser rather than on our servers.

Running a decision needs a LEXUN Key, which is free, needs no card and is not an account: it is a passcode that encrypts your record on your own device, and the decision itself is still never sent to us. Reproducing a published result and reading the accuracy record need nothing at all. What we hold is the email address you give us when you create a Key or join the waitlist, and nothing else. The security page sets out the architecture and the privacy notice sets out the legal position under UK GDPR.

In one sentence: every input carries a label saying whether it is something you measured, something you guessed, or something the model inferred.

These three get blurred together in almost every spreadsheet ever built, and once blurred, a guess acquires the authority of a measurement. Keeping them distinct is what allows the model to widen its bands when it is running mostly on assumptions, and to refuse outright when it is running on nothing else.

In one sentence: a feature that does not exist yet, labelled so on the page rather than described in the present tense.

Every unshipped capability on this site is marked as planned wherever it appears, and the roadmap lists them in one place. There is no ship date attached to most of them, because each is released when it passes its reliability gate and inventing a date would be the same failure this glossary exists to prevent.