The z-value needed to construct a 97.8% confidence interval estimate for the difference between two population proportions is:
A) 2.33
B) 2.29
C) 2.02
D) 1.96
E) 1.65

Question

Quizplus · Accepted Answer

For a 97.8% confidence interval, we need to find the z-value such that there is 0.011 of the distribution to the right of it (since the confidence interval is centered around the sample mean, which is in the middle of the distribution). Using a standard normal table or calculator function, the closest z-value to 0.011 is 2.29, so the answer is B.

The Z-Value Needed to Construct a 97