What is a confidence interval?

A confidence interval is indeed an interval that estimates a population parameter with a specified confidence level. It provides a range within which we can say, with a certain degree of confidence, that the true population parameter (such as a mean or proportion) lies. The confidence level, often expressed as a percentage (like 95% or 99%), indicates how sure we can be about the estimate. For instance, if we calculate a 95% confidence interval for a population mean, it suggests that if we were to take many samples and compute intervals each time, about 95% of those intervals would contain the true population mean.

In statistics, this concept is crucial because it allows researchers to express uncertainty in their estimates. Instead of providing a single point estimate that may not accurately reflect the population, the confidence interval offers a logical range that accounts for sample variability and other factors. This is particularly important in making decisions based on data, as it quantifies the level of certainty associated with the estimate derived from the sample.