Question

Elsie made a one-samlle z interval for a proportion and used the critical value z* = 1.405. What confidence level did she use?

a. 84%

b. 86%

c. 88%

d. 92%

Answer 1

However, If one tailed confidence interval was used, then it should be 92%, because P( z < 1.405) = 0.92. But since generally we used two tailed confidence interval, so above answer with explanation and shaded region was given.

& : P(-1,405< z <1.405): 0.84= 84% Hence if two tailed confidence enterval was used then it should be 84% Z= l6405