What is confidence interval in polling?

• A. A measure of the central tendency of poll results.
• B. The probability that the poll will predict the exact outcome.
• C. The range within which the true population value is expected to lie with a certain level of confidence.
• D. A range that expresses the degree of uncertainty around a poll's estimate, often plus/minus a margin of error.

Answer: (D)

The main idea being tested is how polling expresses uncertainty about an estimate. A confidence interval is not a single number; it’s a range around the poll’s estimate that reflects sampling variability. This interval is typically shown as the estimate plus or minus a margin of error, indicating how wide the possible true value could be if we could repeat the poll many times.

Why this option is the best fits how polls communicate results: it explicitly describes the interval as expressing the degree of uncertainty around the poll’s estimate and mentions the common margin of error used in reporting. This captures both the notion that the true population value could lie within a band, and that the width of that band (the margin of error) reflects how confident we are about the estimate.

The other descriptions don’t capture that practical sense of uncertainty around the poll’s estimate. It’s not about a single central value, it’s not about predicting the exact outcome, and while the formal idea is related, the emphasis in polling reporting is on the range that expresses uncertainty and the margin of error.