Problem 4E

A random sample of 90 observations produced a mean x̄= 25.9 and a standard deviation s= 2.7.

a. Find an approximate 95% confidence interval for the population mean μ.

b. Find an approximate 90% confidence interval for μ.

c. Find an approximate 99% confidence interval for μ.

Answer:

Step 1 of 3:

Given,

a). To find an approximate 95% confidence interval for the population mean

For confidence coefficient 0.95, and

(using the standard normal table, the z value for 95% CI is 1.96)

That is,

The confidence interval is

(25.34, 26.46)

Therefore, the confidence interval is (25.34, 26.46).