$$\text { Find the value of } - \mathrm { z } _{\alpha / 2} \text { that corresponds to a level of confidence of } 98.22 \text { percent. }$$
A)-2.1
B)2.37
C)0.0089
D)-2.37

Question

Quizplus · Accepted Answer

The level of confidence of 98.22% means that the area in the middle of the standard normal distribution is 0.9822, leaving 0.0178 (1 - 0.9822) to be split equally between the two tails. Each tail has an area of 0.0089 (0.0178 / 2). Looking up this area in the z-table to find the z-value that corresponds to the upper tail (since we're dealing with -z), we find that the z-value that leaves an area of 0.0089 in the upper tail is approximately 2.37. Since the question asks for -z, the answer is -2.37.