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Chapter 7: Q 37. (page 462)
More SkittlesWhat sample size would be required to reduce the standard deviation of the sampling distribution to one-half the value you found in Exercise 35(b)? Justify your answer.
Sample size is
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In a certain large population of adults, the distribution of IQ scores is strongly left skewed with a mean of 122 and a standard deviation of 5. Suppose 200 adults are randomly selected from this population for a market research study. For SRSs of size 200, the distribution of sample mean IQ score is
a. left-skewed with mean 122 and standard deviation 0.35.
b. exactly Normal with mean 122 and standard deviation 5.
c. exactly Normal with mean 122 and standard deviation 0.35.
d. approximately Normal with mean 122 and standard deviation 5.
e. approximately Normal with mean 122 and standard deviation 0.35.
refer to the following graph. Here is a dotplot of the adult literacy rates in 177 countries in a recent year, according to the United Nations. For example, the lowest literacy rate was 23.6 %, in the African country of Burkina Faso. Mali had the next lowest literacy rate at 24.0 %.
The overall shape of this distribution is
a. clearly skewed to the right.
b. clearly skewed to the left.
c. roughly symmetric.
d. uniform.
e. There is no clear shape.
The number of hours a lightbulb burns before failing varies from bulb to bulb. The population 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 sampling distribution with the same shape (strongly skewed) as the population distribution.
c. the average burnout time of a large number of bulbs has a sampling distribution with a similar shape but not as extreme (skewed, but not as strongly) as the population distribution.
d. the average burnout time of a large number of bulbs has a sampling distribution that is close to Normal.
e. the average burnout time of a large number of bulbs has a sampling distribution that is exactly Normal.
Increasing the sample size of an opinion poll will reduce the
a. bias of the estimates made from the data collected in the poll.
b. variability of the estimates made from the data collected in the poll.
c. effect of nonresponse on the poll.
d. variability of opinions in the sample.
e. variability of opinions in the population.
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).
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