Consider a normal population distribution with the value of σ known.
(a) What is the confidence level for the interval x ± 2.81σ/ n ? (Round your answer to one decimal place.) %
(b) What is the confidence level for the interval x ± 1.47σ/ n ? (Round your answer to one decimal place.) %
(c) What value of zα/2 in the CI formula below results in a confidence level of 99.7%? (Round your answer to two decimal places.) x − zα/2 · σ n , x + zα/2 · σ n zα/2 = (d) Answer the question posed in part (c) for a confidence level of 78%. (Round your answer to two decimal places.) zα/2 =