Which description correctly distinguishes reliability and external validity?

Which description correctly distinguishes reliability and external validity?

• A. Reliability concerns generalizability; external validity concerns consistency.
• B. Reliability is about sample size only.
• C. External validity measures the speed of data collection.
• D. Reliability determines the theoretical framework.

Answer: (C)

Reliability is about the consistency of a measurement: if you repeat the measurement under the same conditions, you should get similar results. External validity asks whether the findings can be generalized beyond the specific study site, sample, and time—do they apply to other people, settings, and moments? The idea that external validity is about the speed of data collection mixes up logistics with generalizability, which is why that option isn’t correct. Likewise, reliability isn’t defined by sample size alone, nor by determining the theoretical framework. In short, reliability means measurements are repeatable and stable; external validity means the results extend to other contexts beyond the study.

Reliability is about the consistency of a measurement: if you repeat the measurement under the same conditions, you should get similar results. External validity asks whether the findings can be generalized beyond the specific study site, sample, and time—do they apply to other people, settings, and moments?

The idea that external validity is about the speed of data collection mixes up logistics with generalizability, which is why that option isn’t correct. Likewise, reliability isn’t defined by sample size alone, nor by determining the theoretical framework. In short, reliability means measurements are repeatable and stable; external validity means the results extend to other contexts beyond the study.