Question

Consider the one-sided confidence interval expressions for the mean of a normal population. Round your answers to 2 decimal places. (a) What value of z Subscript alpha would result in a 80% one-sided confidence interval? (b) What value of z Subscript alpha would result in a 85% one-sided confidence interval? (c) What value of z Subscript alpha would result in a 90% one-sided confidence interval?

Answer 1

Answer: a) 0.84  b) 0.67  c) 1.28

Step-by-step explanation:

Using the standard normal distribution table for z-value , we have

(a) The value of $z_{\alpha}$ would result in a 80% one-sided confidence interval : $z_{(1-0.80)}=z_{0.20}=0.8416\approx0.84$

(b) The value of $z_{\alpha}$ would result in a 85% one-sided confidence interval : $z_{(1-0.85)}=z_{0.25}=0.6744897\approx0.67$

(c) The value of $z_{\alpha}$ would result in a 90% one-sided confidence interval : $z_{(1-0.90)}=z_{0.10}=1.2815515\approx1.28$