A random sample of 25 employees of a local company has been measured. A 95% confidence interval estimate for the mean systolic blood pressure for all company employees is 123 to 139. Which of the following statements is valid?
A) 95% of the sample of employees has a systolic blood pressure between 123 and 139.
B) If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure.
C) 95% of the population of employees has a systolic blood pressure between 123 and 139.
D) If the sampling procedure were repeated many times, 95% of the sample means would be between 123 and 139.

Question

Quizplus · Accepted Answer

A 95% confidence interval means that if we were to repeat the sampling procedure many times, 95% of the resulting intervals would contain the true population mean. Statement A is incorrect because we cannot make statements about individual members of the sample based on the confidence interval. Statement C is incorrect because we cannot make statements about the population with complete certainty based on a sample. Statement D is incorrect because we cannot make statements about the sample mean based on a confidence interval for the population mean.

A Random Sample of 25 Employees of a Local Company