Concept explainers
(a) Annual returns on the more than 5000 common stocks available to investors vary a lot. In a recent year, the
A. you can get an average return higher than the mean 8.3% by investing in a large number of stocks.
B. as you invest in more and more stocks chosen at random that year, your average return on these stocks gets ever closer to 8.3%.
C. if you invest in a large number of stocks chosen at random, your average return will have approximately a Normal distribution.
D. None of the above.
(b) The number of hours a light bulb burns before failing varies from bulb to bulb. The distribution of burnout times is strongly skewed to the right. The central limit theorem says that
A. as we look at more and more bulbs, their average burnout time gets ever closer to the mean for all bulbs of this type.
B. the average burnout time of a large number of bulbs has a distribution that is close to Normal.
C. the average burnout time of a large number of bulbs has a distribution of the same shape (strongly skewed) as the distribution for individual bulbs.
D. None of the above.
(c) The Bureau of Labor Statistics announces that last month it interviewed all members of the labor force in a sample of 60000 households; 4.9% of the people interviewed were unemployed. The boldface number is a
A. statistic.
B. parameter.
C. sampling distribution.
D. None of the above.
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