Question

The effective life of a component used in a jet-turbine aircraft
engine is a random variable with mean 5000 hours and standard
deviation 40 hours. The distribution of effective life is fairly
close to a normal distribution. The engine manufacturer introduces
an improvement into the manufacturing process for this component
that increases the mean life to 5050 hours and decreases the
standard deviation to 30 hours. Suppose that a random sample of 16
components is selected from the old process and a random sample of
25 components is selected from the improved process. What is the
probability that the difference in the two sample means
μ_{2}-μ_{1} is at least 25 hours?

Answer #1

An electrical component is designed to provide a mean service
life of 4000 hours, with a standard deviation of 800 hours. A
customer purchases a batch of 50 components; assume that this batch
can be considered a simple random sample drawn from the large
population of components. What is the probability that the mean
life for the group of 50 components will be at least 3900
hours?

A machine is adjusted so that the mean of a certain component of
parts used in the aircraft navigation system is 21cm. A random
sample of 12 of these components of the parts revealed a mean of
21.7cm and a standard deviation of 0.3cm? Do these results indicate
that the machine is out of adjustment? Test at the 0.05 level of
significance.

In an electrical circuit, the capacitance of a component should
be between 25 and 40 picofarads (pF). A sample of 25 components
yields a mean of 30 pF and a standard deviation of 3 pF. Calculate
the process capability index Cpk, and comment on the
process performance. If the process is not capable, what proportion
of the product is nonconforming, assuming a normal distribution of
the characteristic?

QUESTION 4: Flying hours for general-aviation
aircraft are normally distributed with a mean of 120 hours. Suppose
we took a random sample of n = 20 aircraft and in that sample we
found the standard deviation as 25 hours. In this sample,
State the sampling distribution of the mean flying hour and the
parameter(s) of the sampling distribution.
What is the probability that the mean flying hour will less
than 110 hours? * ANSWER USING EXCEL FUNCTIONS *
What is...

A
simple random sample of electronic components will be selected to
test for the mean lifetime in hours. Assume that component
lifetimes are normally distributed with population standard
deviation of 31 hours. How many components must be sampled so that
a 99% confidence interval will have margin of error of 6 hours?
Write only an integer as your answer.

1. The lifetime of an
electrical component is modeled as an exponential random variable
with
parameter
b = 2.25 years. A customer has purchased five of these components
and will use one
until the
lifetime is completed, then use the second until that lifetime is
completed, and so on.
Let
Yi ~ exponential (b = 2.25 years) be a random sample of
five components and consider the
total
lifetime T = Y1 + Y2 + Y3...

A random sample of 12 light bulbs has a mean life of 1421 hours
with a standard deviation of 68 hours. Construct a 95% confidence
interval for the mean life, μ, of all light bulbs of this
type. Assume the population has a normal distribution.
Group of answer choices
(1378.2, 1463.8)
(1383.7, 1458.3)
(1382.5, 1459.5)
(1377.8, 1464.2)
(1381.7, 1460.2)

1) A demographer wants to measure life expectancy in countries 1
and 2. Let μ1 and μ2 denote the mean life expectancy in countries 1
and 2, respectively. Specify the hypothesis to determine if life
expectancy in country 1 is more than 10 years lower than in country
2.
A) H0:μ1– μ2≤10, HA:μ1– μ2>10
B) H0:μ1– μ2≥10, HA: μ1– μ2<10
C)H0:μ1– μ2≤–10, HA:μ1– μ2>−10
D)H0:μ1– μ2≥–10, HA:μ1– μ2<−10
2) A restaurant chain has two locations in a medium-sized town
and,...

Power+, produces AA batteries used in remote-controlled toy
cars. The mean life of these batteries follows the normal
probability distribution with a mean of 18 hours and a standard
deviation of 5.4 hours. As a part of its testing program, Power+
tests samples of 25 batteries. Use Appendix B.1 for the
z-values.
a. What can you say about the shape of the
distribution of sample mean?
Shape of the distribution is
(Click to
select) Normal Uniform Binomial
b. What is the standard...

An electronic device factory is studying the length of life of
the electronic components they produced. The manager selects two
assembly lines and takes all samples on those two lines. He got a
sample of 500 electronic components and records the length of life
in the life test. From the sample he found the average length of
life was 200,000 hours and that the standard deviation was 1,000
hours. He wants to find the confidence interval for the average
length...

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