In the context of statistics, which of the following best describes a confidence interval?

• A. A graphical representation of data distribution.
• B. A single value calculated from a sample to estimate a population parameter.
• C. A range of values used to estimate a population parameter with a certain level of confidence.
• D. A measurement that evaluates project performance against its goals.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of a confidence interval. A confidence interval is a range of values, derived from sample data, that is used to estimate an unknown population parameter (e.g., population mean or proportion) with a specified level of confidence (e.g., 95%).
2. Step 2: Recognize that a confidence interval is not a single value but a range. This range is calculated using the sample statistic (e.g., sample mean) and the margin of error, which accounts for variability and uncertainty in the sample data.
3. Step 3: Note that the confidence level (e.g., 95%) indicates the probability that the interval contains the true population parameter if the sampling process were repeated multiple times.
4. Step 4: Eliminate incorrect options. For example, a confidence interval is not a graphical representation of data distribution (this describes a histogram or boxplot), nor is it a single value (this describes a point estimate). It is also not a measurement of project performance.
5. Step 5: Conclude that the correct description of a confidence interval is: 'A range of values used to estimate a population parameter with a certain level of confidence.'