3.4.A—Interpret a confidence interval in context for a population proportion

Interpret a confidence interval in context for a population proportion.

• Because the confidence interval for a population proportion is calculated based on a sample from a population, the computed interval may or may not contain the value of the population proportion.
• The interpretation of the confidence level is that in repeated random sampling with the same sample size, approximately C% of confidence intervals calculated will capture the population proportion, with C representing the numerical value of the confidence level used.
• When interpreting a C% confidence interval for a population proportion, we say we are C% confident that the interval (,ab ) contains the true value of the parameter for the population, where a represents the lower limit and b represents the upper limit. An interpretation of a confidence interval for a population proportion includes a reference to the parameter with details about the population it represents in the context of the study.