Political Prisoners. A 95% confidence interval of 18.4 months to 48.6 months has been found for the mean duration of imprisonment,μ, of political prisoners of a certain country with chronic PTSD.

a. Determine the margin of error, E.

b. Explain the meaning of E in this context in terms of the accuracy of the estimate.

c. Find the sample size required to have a margin of error of 12 months and a 99% confidence level. (Use σ = 45 months.)

d. Find a 99% confidence interval for the mean duration of imprisonment, μ, if a sample of the size determined in part

(c) has a mean of 36.4 months.