In Constructing a Confidence Interval for the Population Mean When $$\bar { X } \pm t _ { a n , n - 1 } ( s / \sqrt { n } )$$

Multiple Choice

In constructing a confidence interval for the population mean when the population variance is unknown, which of the following assumptions is required when using the following formula? $$\bar { X } \pm t _ { a n , n - 1 } ( s / \sqrt { n } )$$

A) The sample size is greater than 30.
B) The population variance is known.
C) The population is normal.
D) The sample is drawn from a positively skewed distribution.