In the Formula $$\bar { X } \pm z _ { a/2 } ( \sigma / \sqrt { n } )$$

Multiple Choice

In the formula $$\bar { X } \pm z _ { a/2 } ( \sigma / \sqrt { n } )$$ , the ?/2 refers to:

A) the probability that the confidence interval will contain the population mean.
B) the probability that the confidence interval will not contain the population mean.
C) the area in the lower tail or upper tail of the sampling distribution of the sample mean.
D) the level of confidence.