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Chapter 7: Q. 55 (page 479)
Songs on an iPod Refer to Exercise 53 . How many songs would you need to sample if you wanted the standard deviation of the sampling distribution of to be 10 seconds? Justify your answer.
The sample should be 36 tracks if the sampling distribution's standard deviation is 10 seconds.
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Unemployment Each month, the Current Population Survey interviews about randomly selected U.S. adults. One of their goals is to estimate the national unemployment rate. In October of those interviewed were unemployed.
Bearings A production run of ball bearings is supposed to have a mean diameter of centimeters (cm). An inspector chooses bearings at random from the run. These bearings have mean diameter cm.
identify the population, the parameter, the sample, and the statistic.
Which of the following statements about the sampling distribution of the sample mean is incorrect?
a. The standard deviation of the sampling distribution will decrease as the sample size increases.
b. The standard deviation of the sampling distribution measures how far the sample mean typically varies from the population mean.
c. The sample mean is an unbiased estimator of the population mean.
d. The sampling distribution shows how the sample mean is distributed around the population mean.
e. The sampling distribution shows how the sample is distributed around the sample mean.
A study of rush-hour traffic in San Francisco counts the number of people in each car entering a freeway at a suburban interchange. Suppose that this count has mean 1.6 and standard deviation 0.75 in the population of all cars that enter at this interchange during rush hour.
a. Without doing any calculations, explain which event is more likely:
b. Explain why you cannot use a Normal distribution to calculate the probability of the first event in part (a).
c. Calculate the probability of the second event in part (a).
Healthy Living From a large group of people who signed a card saying they intended to quit smoking, people were selected at random. It turned out that of these individuals had not smoked over the past months.
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