For each of the following sets of numbers, calculate a 95% confidence interval for the mean (σ known); before calculating the confidence interval, the sample mean (X̅) and standard deviation (s) must be calculated.

a. 7, 5, 8, 7, 4, 6 (assume σ = 1.00)

b. 23, 19, 21, 22, 20, 18, 22, 21 (assume σ = 2.75)

c. 3.05, 2.72, 3.69, 3.11, 2.38, 2.90, 3.37, 2.56, 3.73, 3.02, 2.66 (assume σ = .50)