Which description best defines a confidence interval?

• A. Range of observed sample values
• B. Range in which the true population value is likely to lie
• C. Range of p-values observed
• D. Difference between sample and population means

Answer: (B)

A confidence interval represents a range around a sample estimate that is believed to contain the true population value with a specified level of confidence. It’s built from the data and reflects sampling variability: larger samples or less variability yield tighter intervals, while more variability or smaller samples widen them. The chosen confidence level (for example, 95%) indicates that, if we repeated the study many times, about 95% of the constructed intervals would contain the true parameter. This is not the range of observed data values, nor a range of p-values, nor the difference between the sample and population means. It’s about where the true population value is likely to lie, given the data and the level of certainty.