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Exam 7: Sampling and Sampling Distributions

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Question 81

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Why is the Central Limit Theorem so important to the study of sampling distributions?

A) It allows us to disregard the size of the sample selected when the population is not normal.
B) It allows us to disregard the shape of the sampling distribution when the size of the population is large.
C) It allows us to disregard the size of the population we are sampling from.
D) It allows us to disregard the shape of the population when n is large.

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Question 82

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The Central Limit Theorem is important in statistics because

A) for a large n, it says the population is approximately normal.
B) for any population, it says the sampling distribution of the sample mean is approximately normal, regardless of the sample size.
C) for a large n, it says the sampling distribution of the sample mean is approximately normal, regardless of the shape of the population.
D) for any sized sample, it says the sampling distribution of the sample mean is approximately normal.

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Question 83

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TABLE 7-1 Times spent studying by students in the week before final exams follow a normal distribution with standard deviation 8 hours. A random sample of 4 students was taken in order to estimate the mean study time for the population of all students. -Referring to Table 7-1, what is the probability that the sample mean is more than 3 hours below the population mean?

TABLE 7-4 According to a survey, only 15% of customers who visited the web site of a major retail store made a purchase. Random samples of size 50 are selected. -Referring to Table 7-4, what proportion of the samples will have less than 15% of customers who will make a purchase after visiting the web site?

Items or individuals in a judgment sample are chosen with regard to their probability of occurrence.

A manufacturer of power tools claims that the average amount of time required to assemble their top-of-the-line table saw is 80 minutes with a standard deviation of 40 minutes. Suppose a random sample of 64 purchasers of this table saw is taken. The probability that the sample mean will be less than 82 minutes is ________.

The fact that the sample means are less variable than the population data can be observed from the standard error of the mean.

A population frame for a survey contains a listing of 72,345 names. Using a table of random numbers, how many digits will the code numbers for each member of your population contain?

TABLE 7-6 According to an article, 19% of the entire U.S. population have high-speed access to the Internet. Random samples of size 200 are selected from the U.S. population. -Referring to Table 7-6, among all the random samples of size 200, 90% will have more than ________% who have high-speed access to the Internet.

A sample of size 25 provides a sample variance of 400. The standard error, in this case equal to 4, is best described as the estimate of the standard deviation of means calculated from samples of size 25.

Using different frames to generate data can lead to totally different conclusions.

As the sample size increases, the standard error of the mean increases.

A sample is always a good representation of the target population.

If a simple random sample is chosen with replacement, each individual has the same chance of selection on every draw.

Sampling distributions describe the distribution of

________ results from the exclusion of certain groups of subjects from a population frame.

A manufacturer of power tools claims that the average amount of time required to assemble their top-of-the-line table saw is 80 minutes with a standard deviation of 40 minutes. Suppose a random sample of 64 purchasers of this table saw is taken. The standard deviation of the sampling distribution of the sample mean is ________ minutes.

A sampling distribution is a distribution for a statistic.

The amount of tea leaves in a can from a particular production line is normally distributed with μ = 110 grams and σ = 25 grams. A sample of 25 cans is to be selected. So, the middle 70% of all sample means will fall between what two values?

Major league baseball salaries averaged $3.26 million with a standard deviation of $1.2 million in 2009. Suppose a sample of 100 major league players was taken. What was the standard error for the sample mean salary?