Unisys.com is one of the most frequented business-to-business websites.
According to an article in the Wall Street Journal, business partners accessing Unisys.com spend
an average of 65.7 minutes, possibly the longest average time per visit of any business-to business web site.
Assume that the length of a visit on the Unisys web site is distributed normally with a mean of 65.7 minutes and a standard deviation of 15 minutes.
a) What is the probability that a randomly selected visit will last more than 90 minutes?
b) What is the probability that a randomly selected visit to Unisys.com will last between 60 and 90 minutes?
c) Only 20% of the visits will last less than how many minutes?
d) Between what two values (in minutes) symmetrically distributed around the population mean will 90% of the visit lie?