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AP Research · Unit 3: Method & Data Collection

3.3 Reliability & Validity

Reliability

Reliability is consistency: would the same method give the same results if repeated? A reliable instrument produces stable, repeatable measurements.

Validity

Validity is accuracy: does the method actually measure what it claims to? A test can be reliable (consistent) yet invalid (measuring the wrong thing).

Bias and limitations

Acknowledge sources of bias and limitations in your design — small samples, self-report, researcher influence. Naming limits honestly strengthens your credibility.

Key terms

Reliability
consistency — repeatable results
Validity
accuracy — measures what it claims
Reliable yet invalid
consistent but measuring the wrong thing
Bias
influences that distort results
Limitations
naming them honestly builds credibility

Try an AP-style question

Reliability refers to…

  1. ethics of the study
  2. accuracy of measurement
  3. size of the sample
  4. consistency of results
Show the answer

D. Repeatable.

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