Question

You are constructing a 95% confidence interval using the information: n = 60, x-bar = 65.5, s = 2.5, and E = 0.70. What is the value in the middle of the interval?

Answer 1

65.5

Explanation:

Using the relation :

Xbar ± Margin of error

Margin of Error = Zcritical * s/√n

The Zcritical value at 95% = 1.96

Hence,

Margin of Error = 1.96 * 2.5/√60

Margin of Error = 1.96 * 0.3227486

Margin of Error = 0.6326

Lower boundary = 65.5 - 0.6326 = 64.867

Upper boundary = 65.5 + 0.6326 = 66.133

(64.867 + 66.133) / 2