High concentration of the toxic element arsenic is all too common in groundwater. The article Evaluation of Treatment Systems for the Removal of Arsenic from Groundwater (Practice Periodical of Hazardous, Toxic, and Radioactive Waste Mgmt., 2005: 152157) reported that for a sample of n 5 water specimens selected for treatment by coagulation, the sample mean arsenic concentration was 24.3 g/L, and the sample standard deviation was 4.1. The authors of the cited article used t-based methods to analyze their data, so hopefully had reason to believe that the distribution of arsenic concentration was normal. a. Calculate and interpret a 95% CI for true average arsenic concentration in all such water specimens. b. Calculate a 90% upper confidence bound for the standard deviation of the arsenic concentration distribution. c. Predict the arsenic concentration for a single water specimen in a way that conveys information about precision and reliability.

Chapter 1 Statistics: The Art and Science of Learning From Data 1.1 Using Data to Answer Statistical Questions What is statistics The art and science of learning from data — designing studies, analyzing the data, and translating data into knowledge and understanding of the world around us. Who uses statistics It seems that nearly everyone in every ﬁeld uses statistics in some way shape or form. Some popular examples are sports, medical studies, and marketing. In sports, players are analyzed and give “stats” which represent how good or bad they are at something. Baseball relies on players batting averages to determine how well they perform when hitting. Medical studies utilize statistics almost every day. They use them when determining how effective a treatment is compared to a pre