Download 2. According to a 2014 JD Power report, the mean average monthly

Math 140 Probability Activity#3
Using Statcrunch to find probabilities and x values
for a normal distribution
1. In an effort to increase customer satisfaction, a branch of Bank of America took a random
sample of how long people wait in line at their bank. They found that the wait times were
normally distributed with a mean of 169 seconds and a standard deviation of 36 seconds.
a. What percent of customers are waiting more than 3 minutes (180 seconds)? Do you
think this is a problem for the bank? Why?
b. Find the number of seconds that 20% of customers wait less than.
c. What percent of customers wait between 1 and 2 minutes (60 seconds to 120 seconds)?
d.
Give a recommendation to the bank. Do you believe that customers that complain
about waiting too long have a reason to complain? Why?
2. According to a 2014 JD Power report, the mean average monthly cell phone charges for
Verizon customers is $148 with a standard deviation of $18. Assume that the cell phone
bills are normally distributed.
a) What percent of Verizon customers have a cell phone bill greater than
$100 per month?
b) What percent of Verizon customers have a cell phone bill less than
$175 per month?
c) What are the two cell phone charges that the middle 60% of Verizon customers are
in between?
d) What percent of Verizon customers have a monthly cell phone bill between
$125 and $150?
e) Find the cell phone bill that 90% of Verizon customers pay less than.
f) Find the 67th percentile for cell phone bills. This is the bill that 67% of
Verizon customers are less than.
3. Human pregnancies are normally distributed and last a mean average of 266 days and a
standard deviation of 16 days.
a) What percent of pregnancies last more than 279 days?
b) What percent of pregnancies last less than 251 days?
c) What percent of pregnancies last between 245 days and 272 days?
d) Find the 70th percentile. This is the number of days that 70% of
pregnancies are less than.
e) Find two pregnancy lengths that the middle 80% of people are in
between.