Assessment terms beginning with S

This is a measurement glossary, not a general HR glossary. It covers the vocabulary that appears the moment you open a score report or challenge a vendor's claim — reliability, validity, norms, cut scores, item statistics and fairness analysis — because that is the vocabulary buyers are handed without explanation and the one that decides whether a number can carry a decision.

• Selection ratio

  Also called Selection rate, Hiring ratio

  The selection ratio is the number of people hired divided by the number assessed. It is the lever that decides how much a valid test is worth: the fewer people you take from a given pool, the further up the score distribution your cut falls, and the more predictive accuracy converts into better hires.

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• Social desirability bias

  Also called Faking good, Impression management

  Social desirability bias is the tendency of respondents to answer questionnaires in the way they believe will be viewed favourably rather than accurately. It inflates scores on desirable traits, compresses the differences between people, and is strongest exactly when something depends on the answer — such as a job application.

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• Spearman–Brown formula

  Also called Spearman–Brown prophecy formula, Spearman–Brown prediction formula, Prophecy formula

  The Spearman–Brown formula predicts what a test's reliability would become if it were lengthened or shortened by a given factor. Doubling a test of reliability 0.70 projects 0.82; quadrupling it projects 0.90. It assumes the questions being added are as good as the ones already there, which is the assumption that usually fails.

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• Speeded test

  Also called Speed test, Speeded form

  A speeded test is one whose time limit is tight enough that a meaningful share of candidates never reach the last item, so the score reflects how much correct work was completed rather than how difficult a problem the person could solve. Speed and accuracy are measured together and cannot be separated afterwards.

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• Standard error of measurement

  Also called SEM

  The standard error of measurement is the expected spread of a person's observed scores around their true score if they could be tested repeatedly. It converts a reliability coefficient into the units of the actual scale, which is what turns an abstract number into a usable statement about one individual candidate.

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• Standard error of the difference

  Also called Standard error of the difference between two scores, Standard error of a difference score, SEdiff, Sdiff

  The standard error of the difference is the error attached to the gap between two scores rather than to either score alone. Because both scores carry measurement error, the gap carries both: on a single instrument it is √2 times the standard error of measurement, about 1.41 times wider. A gap under two of them is not a real difference.

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• Standard setting

  Standard setting is the formal process of deciding where a cut score belongs. It uses a documented method — Angoff, bookmark, contrasting groups — with a panel, a written definition of the borderline candidate, and a record of the judgements, so that the resulting threshold can be defended rather than merely asserted.

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• Stanine

  Also called Standard nine

  A stanine is a standardised score on a nine-point scale with a mean of 5 and a standard deviation of 2. The name contracts 'standard nine'. Each stanine covers a fixed slice of the normal distribution, so it reports a person's position deliberately coarsely — in nine bands rather than a hundred percentile points.

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