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Chapter 8: Q. 37 (page 496)
Abstain from drinking Describe a possible source of error that is not included in the margin of error for the confidence interval in Exercise
There are possible sources of errors.
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confidence Find confidence interval using Table A or your calculator. Show your method.
A researcher plans to use a random sample of families to estimate the mean monthly family income for a large population. Aconfidence interval based on the sample would be ______ than a 90% confidence interval.
(a) narrower and would involve a larger risk of being incorrect
(b) wider and would involve a smaller risk of being incorrect
(c) narrower and would involve a smaller risk of being incorrect
(d) wider and would involve a larger risk of being incorrect
(e) wider, but it cannot be determined whether the risk of being incorrect would be larger or smaller
Watching TV (6.1, 7.3) Choose a young person (aged to ) at random and ask, 鈥淚n the past seven days, how many days did you watch television?鈥� Call the response for short. Here is the probability distribution for .
(a) What is the probability that ? Justify your answer.
(b) Calculate the mean of the random variable X. Interpret this value in context.
(c) Suppose that you asked randomly sele
cted young people (aged to ) to respond to the question and found that the mean of their responses was . Would this result surprise you? Justify your answer.
Good wood? A lab supply company sells pieces of Douglas fir inches long and inches square for force experiments in science classes. From experience, the strength of these pieces of wood follows a Normal distribution with standard deviation pounds. You want to estimate the mean load needed to pull apart these pieces of wood to within pounds with confidence. How large a sample is needed? Show your work.
- Understand how the margin of error of a confidence interval changes with the sample size and the level of confidence .
In a poll,
I. Some people refused to answer questions.
II. People without telephones could not be in the sample.
III. Some people never answered the phone in several calls.
Which of these sources is included in the margin of error announced for the poll?
(a) I only
(b) II only
(c) III only
(d) I, II, and III
(e) None of these
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