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Chapter 7: Q.8 (page 429)
How tall? A random sample of female college students has a mean height of inches, which is greater than the -inch mean height of all adult American women.
The value of
Statistic
Parameter .
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Suppose we roll a fair die four times. The probability that a occurs on exactly one of the rolls is
(a)
(b)
(c)
(d)
(e)
Records from a random sample of dairy farms yielded the information below on the number of male and female calves born at various times of the day.
What is the probability that a randomly selected calf was
born in the night or was a female?
(a)
(b)
(c)
(d)
(e)
The student newspaper at a large university asks an SRS of undergraduates, 鈥淒o you favor eliminating the carnival from the term-end celebration?鈥� All in all, of the are in favor. Suppose that (unknown to you) of all undergraduates favor eliminating the carnival. If you took a very large number of SRSs of size from this population, the sampling distribution of the sample proportion would be
(a) exactly Normal with mean and standard deviation of
(b) approximately Normal with mean and standard deviation .
(c) exactly Normal with mean and standard deviation .
(d) approximately Normal with mean and standard deviation .
(e) heavily skewed with mean and standard deviation .
Songs on an iPod David's iPod has about songs. The distribution of the play times for these songs is heavily skewed to the right with a mean of seconds and a standard deviation of seconds.
(a) Explain why you cannot safely calculate the probability that the mean play time is more than minutes seconds for an SRS of songs.
(b) Suppose we take an SRS of songs instead. Explain how the central limit theorem allows us to find the probability that the mean playtime is more than seconds. Then calculate this probability. Show your work.
The number of undergraduates at Johns Hopkins University is approximately , while the number at Ohio State University is approximately . At both schools, a simple random sample of about of the undergraduates is taken. Each sample is used to estimate the proportion p of all students at that university who own an iPod. Suppose that, in fact, at both schools. Which of the following is the best conclusion?
(a) The estimate from Johns Hopkins has less sampling variability than that from Ohio State.
(b) The estimate from Johns Hopkins has more sampling variability than that from Ohio State.
(c) The two estimates have about the same amount of sampling variability.
(d) It is impossible to make any statement about the sampling variability of the two estimates since the students surveyed were different.
(e) None of the above
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