Evidence Quality

A record store that only ever adds rows: corrections are new rows that point at the ones they replace, so history, including the mistake, stays readable.

Looking for, noticing and remembering evidence that supports what we already believe, and discounting what contradicts it.

A third factor that influences both the supposed cause and the outcome, creating or hiding an association between them.

Correlation means two quantities move together; causation means changing one would change the other. Data alone cannot tell which, or whether a third factor drives both.

Confirming a claim with evidence independent of the original source. Reports that trace back to the same origin count as one.

The terms that say what you may do with a dataset or feed: keep a copy, compute from it, publish results, pass it on. Access alone grants none of these.

The recorded path of a piece of data: where it came from, how it was changed, and what depends on it.

Named aspects — accuracy, completeness, consistency, timeliness, uniqueness — that turn the vague idea of clean data into checks you can measure.

A short, dated note made at the time of a decision: options, evidence, assumptions, the choice and what would change it.

Returning, with every score, the reasons behind it: which rules fired, what each criterion contributed and what data were missing.

A ranking of kinds of evidence by how well their design guards against error: reviews and randomised experiments above observational studies, anecdotes at the bottom.

Values that should exist but were not recorded. Why they are missing decides whether ignoring them is harmless or biases the result.

A percentage point is the difference between two percentages; a percent change is that difference relative to the starting value.

Writing down, before seeing results, the question, the data and exactly how it will be analysed, and keeping that record unchanged.

A measurable stand-in for something you cannot measure directly. Proxies work until they become targets: then the number stops tracking what it was meant to represent.

The higher price shown beside the current price to suggest a saving. It is the seller's claim, to be stored separately from the price you pay.

Extreme measurements tend to be followed by less extreme ones, because part of any extreme value is chance. The worst look improved and the best look worse without any cause.

A result is reproducible when someone else, with the same data and code, gets the same result. It needs the data version, code, settings and environment to be recorded.

The units in your data differ systematically from the group you want to describe, because of how they were chosen or kept. Results hold for the selected group only.

A trend that appears in every subgroup can reverse or vanish when the groups are combined, because group sizes differ and the grouping is linked to both choice and outcome.

How far a source deserves to be believed on a given subject: its expertise, access to the facts, track record and incentives. It informs, but never replaces, checking the claim.

A selection error from studying only what survived a process and ignoring what dropped out along the way.

Material produced once and published by many outlets, such as a news-agency story. Counting every publication overstates how many independent sources reported something.

A platform that connects two groups, such as buyers and sellers. Its rules for listing, ranking and fees shape the numbers it publishes.

A standard file format that stores the raw requests and responses of web captures together with when and how each was made.