Refer to the Chance (Summer 2007) article on phishing attacks at a company, Exercise 2.33. Recall that phishing describes an attempt to extract personal/financial information through fraudulent e-mail. The company set up a publicized e-mail account-called a "fraud box" that enabled employees to notify them if they suspected an e-mail phishing attack. If there is minimal or no collaboration or collusion from within the company, the inter arrival times (i.e., the time between successive e-mail notifications, in seconds) have an approximate exponential distribution with a mean of 95 seconds.
a. What is the probability of observing an inter arrival time of at least 2 minutes?
b. Data for a sample of 267 inter arrival times are saved in the accompanying file. Do the data appear to follow an exponential distribution with θ = 95?