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Chapter 8: Q.14 (page 478)
In words, define the random variable .
- the weight in kilograms of the heads of lettuce.
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The standard deviation of the weights of elephants is known to be approximately pounds. We wish to construct a % confidence interval for the mean weight of newborn elephant calves. Fifty newborn elephants are weighed. The sample mean is 244 pounds . The simple standard deviation is 11 pounds.
1. Identify the following:
a. x- = _____
b. 蟽= _____
c. n= _____
Identify the following:
a. x=_______
b. sx =_______
c. n =_______
d. n 鈥� 1 =_______
A telephone poll of adult Americans was reported in an issue of Time Magazine. Another question in the poll was 鈥淸How much are] you worried about the quality of education in our schools?鈥� Sixty-three percent responded 鈥渁 lot鈥�. We are interested in the population proportion of adult Americans who are worried a lot about the quality of education in our schools.
a. Define the random variables and in words.
b. Which distribution should you use for this problem? Explain your choice.
c. Construct a confidence interval for the population proportion of adult Americans who are worried a lot about the quality of education in our schools.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
d. The sampling error given by Yankelevich Partners, Inc. (which conducted the poll) is . In one to three complete sentences, explain what the represents.
Suppose that a committee is studying whether or not there is waste of time in our judicial system. It is interested in
the mean amount of time individuals waste at the courthouse waiting to be called for jury duty. The committee randomly
surveyed people who recently served as jurors. The sample mean wait time was eight hours with a sample standard
deviation of four hours.
b. Define the random variables in words.
c. Which distribution should you use for this problem? Explain your choice.
d. Construct a confidence interval for the population mean time wasted.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
e. Explain in a complete sentence what the confidence interval means.
Unoccupied seats on flights cause airlines to lose revenue. Suppose a large airline wants to estimate its mean number of unoccupied seats per flight over the past year. To accomplish this, the records of 225 flights are randomly selected and the number of unoccupied seats is noted for each of the sampled flights. The sample mean is 11.6 seats and the sample standard deviation is 4.1 seats.
a. i. __________
ii. __________
iii. __________
iv. __________
b. Define the random variables and in words.
c. Which distribution should you use for this problem? Explain your choice.
d. Construct a 92% confidence interval for the population mean number of unoccupied seats per flight.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
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