4.2.D—Calculate an appropriate confidence interval for a population mean or population mean difference

Calculate an appropriate confidence interval for a population mean or population mean difference.

• A point estimate for a population mean is the sample mean, x, or xd for the sample mean difference.
• To estimate the population mean for one sample or the population mean difference between values in matched pairs, when the population standard deviation is unknown, the confidence interval is * sx±t n , where t∗ is the critical value for the central C% of a t-distribution with degrees of freedom n −1.