What is the role of sample size in evaluating evidence?

• A. It has no impact on reliability.
• B. A larger, representative sample generally increases reliability.
• C. Sample size only matters for qualitative research.
• D. A smaller sample is always better for speed.

Answer: (B)

Sample size determines how trustworthy evidence is. A larger, representative sample tends to make estimates more reliable because random fluctuations cancel out as you gather more data. This reduces sampling error and increases precision, so the results better reflect the true characteristics of the population and are more generalizable. When the sample is big and well chosen to mirror the population, you gain confidence that the findings aren’t just due to chance or a odd subset.

If the sample is too small or biased, results can mislead by exaggerating effects or missing important variation. Statements that there’s no impact from sample size ignore sampling variance; claims that it only matters for qualitative research miss that reliability and generalizability are affected in both types of study; and the idea that a smaller sample is always better for speed sacrifices the quality of the evidence.