A random sample of n measurements was selected from a 1) population with unknown mean μ and standard deviation σ=20. Calculate a 95% confidence interval for μ for each of the following situations: a. n=75,xˉ=28 b. n=200,xˉ=102 c. n=100,xˉ=15 d. n=100,xˉ=4.05 e. Is the assumption that the underlying population of measurements is normally distributed necessary to ensure the validity of the confidence intervals in parts a-d? Explain.