What is the confidence level?

What is the confidence level?

• A. Index of certainty
• B. Difference in the values are among groups
• C. Indicator of chance occurrence
• D. Index of randomization

Answer: (A)

Confidence level describes how much trust we place in an interval estimate. It is the probability, over many repeated samples, that the interval calculated from the data would contain the true population parameter. For example, a 95% confidence level means that if you repeated the study many times and computed a confidence interval each time, about 95% of those intervals would include the true value. It’s not about the likelihood that this single interval contains the parameter—the parameter is fixed—but about the long-run performance of the method used to generate intervals. The other ideas relate to different concepts: differences among groups refer to effect size or group comparisons; an indicator of chance occurrence points to a p-value or significance; and an index of randomization concerns how subjects were assigned to groups.

Confidence level describes how much trust we place in an interval estimate. It is the probability, over many repeated samples, that the interval calculated from the data would contain the true population parameter. For example, a 95% confidence level means that if you repeated the study many times and computed a confidence interval each time, about 95% of those intervals would include the true value. It’s not about the likelihood that this single interval contains the parameter—the parameter is fixed—but about the long-run performance of the method used to generate intervals. The other ideas relate to different concepts: differences among groups refer to effect size or group comparisons; an indicator of chance occurrence points to a p-value or significance; and an index of randomization concerns how subjects were assigned to groups.