You are looking for antonyms and synonyms for random sample?

A synonym for "random sample" is "probability sample," as both refer to a selection method that ensures each member of a population has an equal chance of being chosen. An antonym could be "non-random sample" or "biased sample," which indicates a selection process that does not provide equal opportunity for all members of the population. These terms highlight the contrast between systematic, unbiased selection and arbitrary or selective methods.