Find the critical value $z _ { \alpha / 2 }$ needed to construct a(n) 80% confidence interval.
A) 0.84
B) 1.08
C) 1.28
D) 2.10

Question

Find the critical value $z _ { \alpha / 2 }$ needed to construct a(n)  80%  confidence interval.
A)  0.84 
B)  1.08 
C)  1.28 
D)  2.10

Quizplus · Accepted Answer

For an 80% confidence interval, the area in each tail of the normal distribution is 10% (100% - 80% = 20%, divided by 2 because it's two-tailed). The z-score that corresponds to the area to the left of 90% (or 0.9) in the standard normal distribution is approximately 1.28.

Find the Critical Value zα/2z _ { \alpha / 2 }zα/2​

Find the Critical Value $z _ { \alpha / 2 }$