Do One of the Following, as Appropriate:
(A) Find $z _ { \alpha / 2 }$

Multiple Choice

Do one of the following, as appropriate:
(a) Find the critical value $z _ { \alpha / 2 }$
(b) find the critical value $t _ { \alpha / 2 }$
99% ; n=17 ; $\alpha$

is unknown; population appears to be normally distributed.

A) $z _ { \sigma / 2 } = 2.583$
B) $z _ { \sigma / 2 } = 2.567$
C) $t _ { \sigma / 2 } = 2.921$
D) $t _ { \sigma / 2 } = 2.898$