Chapter 8, Section 8.3, Problem 13b The standard deviation for a population is ? = 15.3. A sample of 36 observations selected from this population gave a mean equal to 75.1. Round your answers to 2 decimal places. Construct a 95% confidence interval for ?. Solution =15.3 n=36 =75.1 z(/2)=1.96 95% CI is: (75.1-1.96*15.3/36,75.1+1.96*15.3/36)=(75.1-5,75.1+5)=(70.1,80.1).