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Which of the following statements about the sampling distribution of the sample mean, x-bar, is not true? A. The distribution is normal regardless of the shape of the population distribution, as long as the sample size, n, is large enough. B. The distribution is normal regardless of the sample size, as long as the population distribution is normal. C. The distribution's mean is the same as the population mean. D. The distribution's standard deviation is smaller than the population standard deviation. E. All of the above statements are correct.
Suppose that a candy company makes a candy bar whose weight is supposed to be 50 grams, but in fact, the weight varies from bar to bar according to a normal distribution with mean μ = 50 grams and standard deviation σ = 2 grams.
If the company sells the candy bars in packs of 4 bars, what can we say about the likelihood that the average weight of the bars in a randomly selected pack is 4 or more grams lighter than advertised?
A. There is no way to evaluate this likelihood, since the sample size (n = 4) is too small. B. There is about a 16% chance of this occurring. C. There is about a 5% chance of this occurring. D. There is about a 2.5% chance of this occurring. E. It is extremely unlikely for this to occur; the probability is very close to 0.
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发表于 2013-7-6 17:44:16
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