Seven Hills Hospital in Visakhapatnam, Andhra Pradesh, commonly conducts stress tests to study the heart muscle after a person has a heart attack. Members of the diagnostic imagine department conducted a quality improvement project with the objective of reducing the turnaround time for stress tests. Turnaround time is defined as the time from when a test is ordered to when the radiologist signs off on the test results. Initially, the mean turnaround time for a stress-test was 68 hours. After incorporating changes into the stress-tress process, the quality improvement team collected a sample of 50 turnaround times. In this sample, the mean turnaround time was 32 hours, with a standard deviation of 9 hours. 1. Construct a 95% confidence interval estimate for the population mean turnover time. 2. Interpret the interval constructed in (a). 3.   Do you think the quality improvement project was a success? Customers experiencing technical difficulty with their internet cable hookup may call an 800 number for technical support. It takes the technician between 30 seconds to 15 minutes to resolve the problem. The distribution of this support time follows the uniform distribution. (a) What are the values for a andb in minutes? (Do not round your intermediate calculations. Round your answer to 1 decimal place.)   a   b (b-1) What is the mean time to resolve the problem? (Do not round your intermediate calculations. Round your answer to 2 decimal places.)   Mean (b-2) What is the standard deviation of the time? (Do not round your intermediate calculations. Round your answer to 2 decimal places.)   Standard deviation (c) What percent of the problems take more than 5 minutes to resolve? (Do not round your intermediate calculations. Round your answer to 2 decimal places. Omit the "%" sign in your response.)   Percent %   (d) Suppose we wish to find the middle 50 percent of the problem-solving times. What are the end points of these two times? (Do not round your intermediate calculations. Round your answers to 3 decimal places.)   End point 1   End point 2 2. A normal population has a mean of 21 and a standard deviation of 5. (a) Compute the z value associated with 25 (Round your answer to 2 decimal places.) Z (b) What proportion of the population is between 21 and 25? (Round z-score computation to 2 decimal places and your final answer to 4 decimal places.)   Proportion (c) What proportion of the population is less than 17? (Round z-score computation to 2 decimal places and your final answer to 4 decimal places.) 3.   Proportion The number of viewers of American Idol has a mean of 23 million with a standard deviation of 8 million. Assume this distribution follows a normal distribution. What is the probability that next week's show will: (a) Have between 28 and 32 million viewers? (Round z-score computation to 2 decimal places and your final answer to 4 decimal places.)   Probability (b) Have at least 17 million viewer.

1. Seven Hills Hospital in Visakhapatnam, Andhra Pradesh,
commonly conducts stress tests to study the heart muscle after a
person has a heart attack. Members of the diagnostic imagine
department conducted a quality improvement project with the
objective of reducing the turnaround time for stress tests.
Turnaround time is defined as the time from when a test is
ordered to when the radiologist signs off on the test results.
Initially, the mean turnaround time for a stress-test was 68
hours. After incorporating changes into the stress-tress process,
the quality improvement team collected a sample of 50
turnaround times. In this sample, the mean turnaround time was
32 hours, with a standard deviation of 9 hours.
1. Construct a 95% confidence interval estimate for the
population mean turnover time.
2. Interpret the interval constructed in (a).
3. Do you think the quality improvement project was a
success?
Customers experiencing technical difficulty with their internet
cable hookup may call an 800 number for technical support. It
takes the technician between 30 seconds to 15 minutes to
resolve the problem. The distribution of this support time
follows the uniform distribution.
(a)
What are the values for a andb in minutes? (Do not round your
intermediate calculations. Round your answer to 1 decimal
place.)
a

2. b
(b-1)
What is the mean time to resolve the problem? (Do not round
your intermediate calculations. Round your answer to 2 decimal
places.)
Mean
(b-2)
What is the standard deviation of the time? (Do not round your
intermediate calculations. Round your answer to 2 decimal
places.)
Standard deviation
(c)
What percent of the problems take more than 5 minutes to
resolve? (Do not round your intermediate calculations. Round
your answer to 2 decimal places. Omit the "%" sign in your
response.)
Percent
%
(d)
Suppose we wish to find the middle 50 percent of the problem-
solving times. What are the end points of these two times? (Do
not round your intermediate calculations. Round your answers
to 3 decimal places.)

3. End point 1
End point 2
2.
A normal population has a mean of 21 and a standard deviation
of 5.
(a)
Compute the z value associated with 25 (Round your answer to
2 decimal places.)
Z
(b)
What proportion of the population is between 21 and 25?
(Round z-score computation to 2 decimal places and your final
answer to 4 decimal places.)
Proportion
(c)
What proportion of the population is less than 17? (Round z-
score computation to 2 decimal places and your final answer to
4 decimal places.)
3.
Proportion

4. The number of viewers of American Idol has a mean of 23
million with a standard deviation of 8 million. Assume this
distribution follows a normal distribution.
What is the probability that next week's show will:
(a)
Have between 28 and 32 million viewers? (Round z-score
computation to 2 decimal places and your final answer to 4
decimal places.)
Probability
(b)
Have at least 17 million viewers? (Round z-score computation
to 2 decimal places and your final answer to 4 decimal places.)
Probability
(c)
Exceed 40 million viewers? (Round z-score computation to 2
decimal places and your final answer to 4 decimal places.)
Probability
4
Among U.S. cities with a population of more than 250,000 the
mean one-way commute to work is 24.3 minutes. The longest
one-way travel time is New York City, where the mean time is
38.8 minutes. Assume the distribution of travel times in New
York City follows the normal probability distribution and the

5. standard deviation is 7.7 minutes.
(a)
What percent of the New York City commutes are for less than
27 minutes? (Round the intermediate values to 2 decimal places.
Round your answers to 2 decimal places. Omit the "%" sign in
your response.)
Percent
%
(b)
What percent are between 27 and 35 minutes? (Round the
intermediate values to 2 decimal places. Round your answers to
2 decimal places. Omit the "%" sign in your response.)
Percent
%
(c)
What percent are between 27 and 43 minutes? (Round the
intermediate values to 2 decimal places. Round your answers to
2 decimal places. Omit the "%" sign in your response.)
Percent
%
5.
Assume that the mean hourly cost to operate a commercial
airplane follows the normal distribution with a mean of $2,025
per hour and a standard deviation of $195.
What is the operating cost for the lowest 3 percent of the
airplanes? (Round z value to 2 decimal places. Omit the "$"
sign in your response.)
1658.40

6. 6.
For the most recent year available, the mean annual cost to
attend a private university in the United States was $20,307.
Assume the distribution of annual costs follows the normal
probability distribution and the standard deviation is $4,275.
Ninety-five percent of all students at private universities pay
less than what amount? (Round z value to 2 decimal places and
your final answer to the nearest whole number. Omit the "$"
sign in your response.)
7.
Dottie's Tax Service specializes in federal tax returns for
professional clients, such as physicians, dentists, accountants,
and lawyers. A recent audit by the IRS of the returns she
prepared indicated that an error was made on 7 percent of the
returns she prepared last year. Assuming this rate continues into
this year and she prepares 80 returns. What is the probability
that she makes errors on:
(a)
More than 6 returns? (Round z-score computation to 2 decimal
places and your final answer to 4 decimal places.)
Probability
(b)
At least 6 returns? (Round z-score computation to 2 decimal
places and your final answer to 4 decimal places.)
Probability
(c)
Exactly 6 returns? (Round z-score computation to 2 decimal
places and your final answer to 4 decimal places.)

7. Probability
8.
Waiting times to receive food after placing an order at the local
Subway sandwich shop follow an exponential distribution with a
mean of 52 seconds. Calculate the probability a customer waits:
0_13_2011
(a)
Less than 32 seconds. (Round your answer to 4 decimal places.)
Probability
rev: 10_13_2011
check my workeBookLinkreferences
(b)
More than 120 seconds. (Round your answer to 4 decimal
places.)
Probability
rev: 10_13_2011
check my workeBookLinkreferences
(c)
Between 40 and 65 seconds. (Round your answer to 4 decimal
places.)
Probability

8. rev: 10_13_2011
check my workeBookLinkreferences
(d)
Fifty percent of the patrons wait less than how many seconds?
What is the median? (Round youranswer to 2 decimal places.)
Median
seconds
9.
The Bureau of Labor Statistics’ American Time Use Survey
showed that the amount of time spent using a computer for
leisure varied greatly by age. Individuals age 75 and over
averaged .30 hour (18 minutes) per day using a computer for
leisure. Individuals ages 15 to 19 spend 1.0 hour per day using a
computer for leisure. If these times follow an exponential
distribution, find the proportion of each group that spends:
_13_2011
(a)
Less than 14 minutes per day using a computer for leisure.
(Round your answers to 4 decimal places.)
Proportion
and
rev: 10_13_2011

9. (b)
More than two hours. (Round your answers to 4 decimal places.)
Proportion
and
rev: 10_13_2011
(c)
Between 28 minutes and 84 minutes using a computer for
leisure. (Round your answers to 4 decimal places.)
Proportion
and
(d)
Find the 28th percentile. Seventy two percent spend more than
what amount of time? (Round your answers to 2 decimal
places.)
Amount of time for individuals age 75 and over
minutes
Amount of time for individuals ages 15 to 19
minutes
10.
The cost per item at a supermarket follows an exponential
distribution. There are many inexpensive items and a few
relatively expensive ones. The mean cost per item is $10.00.

10. What is the percentage of items that cost:
r
(a)
Less than $7.00? (Round your answer to 4 decimal places.)
Probability
rev: 10_132011
(b)
More than $11.00? (Round your answer to 4 decimal places.)
Probability
(c)
Between $8.00 and $10.00? (Round your answer to 4 decimal
places.)
Probability
(d)
Find the 50th percentile. Fifty percent of the supermarket items
cost more than what amount? (Round youranswer to 2 decimal
places.)
Amount
$

11. 1