accuracy

Meaning: Accuracy is the closeness of a measurement or conclusion to the true value of what is being studied. In psychology and sociology it is usually discussed through validity: does the test, survey, or study measure what it claims to measure? Reliability is a different property, the consistency of results across repeated trials, raters, or time. Systematic error (bias), such as a leading survey question or social desirability bias in self-reports, pushes results away from the truth in one direction and lowers accuracy. Random error scatters results and lowers reliability. (Physics and chemistry labs use accuracy versus precision in the same way.)

On the MCAT: A passage describes a questionnaire, scale, or observational measure and asks whether it is reliable, valid, or both. You may need to spot the flaw, for example scores that are stable on retesting but miss the intended construct (reliable but not valid), or scores that vary widely between raters (low reliability). Biased sampling and vague operational definitions also undermine how accurately results apply to the population.

Common confusion: Students treat reliable as meaning accurate. Consistent results can all be wrong by the same bias, like a scale that reads 2 kg too high every time. Reliability is usually necessary for validity but does not guarantee it.