# covariate shift

CEFR C2 · Noun

Source: https://englishreference.com/word/covariate-shift
Updated: 2026-09-28

## Definition

a specific problem where input data looks different, but the fundamental rules connecting inputs to answers stay the same.

For teachers: a specialized form of distribution shift where the marginal distribution of input covariates changes between train and test, while conditional label distributions remain invariant.

## Examples

- A model trained on adult speech struggled with children's voices due to covariate shift, even though the words were identical.
- Importance weighting techniques correct for covariate shift by reweighting training samples to match deployment input frequencies.
- In clinical AI deployment, covariate shift arises when patient demographics differ across hospitals even though underlying disease etiologies remain constant.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.