De Anza College Elementary Statistics Solution Process Exercises All the questions need full solution process, I don’t need just the answers. Moreover, I a

De Anza College Elementary Statistics Solution Process Exercises All the questions need full solution process, I don’t need just the answers. Moreover, I add the right answers at the end, whe you finish, you can check that. VERY IMPORTANT: I need the full solution process, thanks. Lecture 16
Homework
For all the homework problems, assume that the population follows a normal distribution.
Suppose it is required that the mean operating life for size `D’ batteries be 22 hours. If a
random sample of 16 batteries has a mean operating life of 20 hours and a standard deviation of
4 hours, can we conclude that the mean operating life of `D’ batteries is not 22 hours? Answer:
p-value = 0.0639 (9.1.4)
1.
A certain printing press is known to turn out an average of 45 copies per minute. An adjustment
is made to the machine in at attempt to increase its output. In 10 randomly selected test runs, it
turns out an average of 47 copies per minute with a sample standard deviation of 2. For = 0.01,
can it be claimed that the adjustment was successful? Explain. Answer: p-value = 0.00575
(9.1.6)
2.
An industrial company claims that the mean pH level of the water in a nearby river is 6.8. You
randomly select 19 water samples and measure the pH of each. The sample mean and standard
deviation are 6.7 and 0.24, respectively. Is there enough evidence to reject the company’s claim at
= 0.05? Assume the population is normally distributed. Answer: p-value = 0.0861 (F & L
7.3.E5)
3.
As part of your work for an environmental awareness group, you want to test a claim that the
mean waste generated by adults in the United States is more than 4 pounds per day. In a random
sample of 10 adults in the United States, you nd that the mean waste generated per person per
day is 4.54 pounds with a standard deviation of 1.21 pounds. At = 0.05, can you support the
claim? Answer: p-value = 0.0959 (F & L 7.3.26)
4.
Suppose a random sample of 16 observations gives a sample mean of 18.5. At a con dence level
of 98%, the con dence interval about the population mean is (16.5, 20.5).
(a) What is the error bound? Answer: error bound = 2
(b) What is s? Answer: s = 3.074 (9.2.1)
5.
A random sample of 25 elementary statistics students gives an average of 72 on the rst midterm
with a standard deviation of 10. Find the 95% con dence interval for the population mean of rst
midterm scores. Answer: (67.872, 76.128) (9.2.2)
6.
A researcher claims that adult German Shepherd male dogs fed a special diet have an average
weight of 85 pounds. A random sample of 12 such dogs shows an average weight of 83.2 pounds
with a standard deviation of 2.5 pounds.
(a) Test an appropriate hypotheses. Use a signi cance level of 0.05. Answer: p-value = 0.0298
(b) Find the 95% con dence interval for the true mean weight. Answer: (81.612, 84.788) (9.2.7)
7.
Homes in a nearby college town have a mean value of 158,950 dollars. It is assumed that the
homes in the vicinity of the college have a higher value. To test this claim, a random sample of 16
homes is chosen from around the college. Their mean valuation is 162,460 dollars and the sample
standard deviation is 5,400 dollars. Compute a 90% con dence interval for the true mean value of
homes. (9.P.10) Answer: (160093.382, 164826.618)
8.
Reminder:
The con dence interval is a function of the sample mean.
You work for a consumer advocate agency and want to nd the mean repair cost of a washing
machine. As part of your study, you randomly select 40 repair costs and nd the mean to be 120
dollars. The sample standard deviation is $17.50. Construct a 95% con dence interval for the
population mean repair cost. Answer: (114.403, 125.597)
9.
A publisher wants to estimate the mean length of time (in minutes) all adults spend reading
newspaper. To determine this estimate, the publisher takes a random sample of 7 people and
obtains the follow results: 11, 9, 8, 10, 10, 9, 7. Construct a 99% con dence interval for the
population mean length of time. Answer: (7.258, 11.028)
10.
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