Chilled cast iron is used for mechanical components that need particularly high levels of hardness and durability. In an experiment to investigate the corrosion properties of a particular type of chilled cast iron, a collection of x = 10 samples of this chilled cast iron provided corrosion rates with a sample mean of x- = 2.752 and a sample standard deviation of s = 0.280. Construct a two-sided 99% confidence interval for the average corrosion rate for chilled cast iron of this type. Is 3.1 a plausible value for the average corrosion rate? (This problem is continued in Problem 8.2.15.)
for Problems 8.1.18-8.1.22 use the summary statistics that you calculated for the data sets to construct by hand confidence intervals for the appropriate population mean. Use your statistical software package to obtain confidence intervals and check your answers. Show how you would describe what you have learned from your analysis.