What is sampling bias?

What is sampling bias?

• A. Bias only affects internal validity.
• B. Sampling bias occurs when the sample is not representative of the population; it undermines generalizability.
• C. Sampling bias is desirable to focus on a subgroup.
• D. The sample is always representative.

Answer: (B)

Sampling bias happens when the way you select participants causes the sample to systematically differ from the population you want to describe. Because the sample isn’t truly representative, the findings don’t accurately reflect the whole population, so you can’t generalize the results. This is exactly what the statement means: the sample isn’t representative of the population, and that lack of representativeness undermines generalizability (external validity). The other ideas are off: bias isn’t only about internal validity, and it's not desirable to focus on a subgroup in a way that skews results. And saying the sample is always representative is simply false. For a study to generalize well, the sample needs to resemble the population in key characteristics.

Sampling bias happens when the way you select participants causes the sample to systematically differ from the population you want to describe. Because the sample isn’t truly representative, the findings don’t accurately reflect the whole population, so you can’t generalize the results.

This is exactly what the statement means: the sample isn’t representative of the population, and that lack of representativeness undermines generalizability (external validity). The other ideas are off: bias isn’t only about internal validity, and it's not desirable to focus on a subgroup in a way that skews results. And saying the sample is always representative is simply false. For a study to generalize well, the sample needs to resemble the population in key characteristics.