The Formula for a 100(1 - α)% Confidence Interval for the Mean

Multiple Choice

The formula for a 100(1 - α) % confidence interval for the mean μ when the population standard deviation is unknown is ________.

A) $x_{i}-\bar{x} /(\sigma / \sqrt{n})$

B) $\bar{x} \pm t_{\alpha} / 2 n-1(s / \sqrt{n})$

C) $\bar{x} \pm_{z} \alpha / 2(\sigma / \sqrt{n})$

D) $-\frac{(\sigma / \sqrt{n}) }{z \alpha / 2}$