Chapter 13.4, Problem 42E

For the cereal data of the previous exercise, the mean x value is 19.21. Would a 95% confidence interval with x* = 20 or x* = 17 be wider? Explain. Answer the same question for a prediction interval.

13.45 The shelf life of packaged food depends on many factors. Dry cereal is considered to be a moisture-sensitive product (no one likes soggy cereal!) with the shelf life determined primarily by moisture content. In a study of the shelf life of one particular brand of cereal, x = Time on shelf (days stored at 73°F and 50% relative humidity) and y = Moisture content (%) were recorded. The resulting data are from “Computer Simulation Speeds Shelf Life Assessments” (Package Engineering [1983]: 72–73).