Chapter 3.4, Problem 31AYU

Fraud Detection Revisited Use the fraud-detection data from Problem 25 to do the following.

1. a. Determine the standard deviation and interquartile range of the data.
2. b. Suppose the month in which the customer used 346 minutes was not actually that customer’s phone. That particular month, the customer did not use her phone at all, so 0 minutes were used. How does changing the observation from 346 to 0 affect the standard deviation and interquartile range? What property does this illustrate?

25. Fraud Detection As part of its “Customers First” program, a cellular phone company monitors monthly phone usage. The program identifies unusual use and alerts the customer that their phone may have been used by another person. The data below represent the monthly phone use in minutes of a customer enrolled in this program for the past 20 months. The phone company decides to use the upper fence as the cutoff point for the number of minutes at which the customer should be contacted. What is the cutoff point?