Assessment terms beginning with P

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.

• Percentile

  Also called Percentile rank

  A percentile is a position, not a proportion. A percentile of 70 means the person scored at or above 70 per cent of the norm group; it does not mean they answered 70 per cent of the questions correctly. Percentiles are also compressed in the middle of a distribution and stretched at the extremes.

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• Predictive validity

  Predictive validity is the correlation between a score measured before a hiring decision and an outcome measured afterwards, such as supervisor-rated performance. It is the form of validity evidence that matters most in selection, because it is the only one whose study design matches the way the test is actually used.

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• Psychometrics

  Psychometrics is the science of measuring psychological attributes — ability, personality, knowledge, attitude — that cannot be observed directly. It covers how questions are written and calibrated, how responses become scores, how much error surrounds a score, and what evidence is required before a score may support a decision about a person.

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