Chapter 7.2, Problem 18E

The U.S. Army commissioned a study to assess how deeply a bullet penetrates ceramic body armor (“Testing Body Armor Materials for Use by the U.S. Army-Phase III,” 2012). In the standard test, a cylindrical clay model is layered under the armor vest. A projectile is then fired, causing an indentation in the clay. The deepest impression in the clay is measured as an indication of survivability of someone wearing the armor. Here is data from one testing organization under particular experimental conditions; measurements (in mm) were made using a manually controlled digital caliper:

1. a. Construct a boxplot of the data and comment on interesting features.
2. b. Construct a normal probability plot. Is it plausible that impression depth is normally distributed? Is a normal distribution assumption needed in order to calculate a confidence interval or bound for the true average depth μ using the foregoing data? Explain. Use the accompanying Minitab output as a basis for calculating and interpreting an upper confidence bound for μ with a confidence level of 99%.

Variable	Count	Mean	SE Mean	StDev
Depth	83	33.370	0.578	5.268

Q1	Median	Q3	IQR
30.400	33.500	36.000	5.600