What is margin of error?

• A. The percent that represents how many respondents were nonresponse.
• B. The range by which the sample size affects the vote share.
• C. The range within which the true population value is expected to lie with a certain level of confidence.
• D. The probability that the poll is biased.

Answer: (C)

Margin of error is the range around an estimate that expresses how far the true population value could be because you’re using a sample rather than the entire group. It’s tied to a chosen level of confidence, like 95%, meaning if you repeated the process many times, about 95% of the intervals you calculate would contain the true value. For example, a poll might report 52% support with a margin of error of ±3 percentage points, implying the true support is likely between 49% and 55% at that confidence level. This concept reflects sampling variability, not bias or nonresponse. Larger samples shrink the margin of error, while higher confidence levels widen it, and more variability in responses increases it.