Chapter 7: Q. 7.29 (page 300)
Does the sample size have an effect on the standard deviation of all possible sample means? Explain your answer.
Short Answer
Yes, the sample size has an effect on the standard deviation of all possible sample means.
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Chapter 7: Q. 7.29 (page 300)
Does the sample size have an effect on the standard deviation of all possible sample means? Explain your answer.
Yes, the sample size has an effect on the standard deviation of all possible sample means.
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According to the central limit theorem, for a relatively large sample size, the variable is approximately normally distributed.
a. What rule of thumb is used for deciding whether the sample size is relatively large?
b. Roughly speaking, what property of the distribution of the variable under consideration determines how large the sample size must be for a normal distribution to provide an adequate approximation to the distribution of ?
Ethanol Railroad Tariffs. An ethanol railroad tariff is a fee charged for shipments of ethanol on public railroads. The Agricultural Marketing Service publishes tariff rates for railroad-car shipments of ethanol in the Biofuel Transportation Database. Assuming that the standard deviation of such tariff rates is , determine the probability that the mean tariff rate of randomly selected railroad car shipments of ethanol will be within of the mean tariff rate of all railroad-car shipments of ethanol. Interpret your answer in terms of sampling error.
Paint Durability. A paint manufacturer in Pittsburgh claims that his paint will last an average of years. Assuming that paint life is normally distributed and has a standard deviation of year. answer the following questions:
a. Suppose that you paint one house with the paint and that the paint lasts years. Would you consider that evidence against the manufacturer's claim? (Hint: Assuming that the manufacturer's claim is correct, determine the probability that the paint life for a randomly selected house painted with the paint is years or less.)
b. Suppose that you paint houses with the paint and that the paint lasts an average of years for the houses. Would you consider that evidence against the manufacturer's claim?
c. Repeat part (b) if the paint lasts an average of years for the houses painted.
7.2 Why should you generally expect some error when estimating a parameter (e.g., a population mean) by a statistic (e.g., a sample mean)? What is this kind of error called?
Why is obtaining the mean and standard deviation of a first step in approximating the sample distribution of the sample mean by a normal distribution?
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