23、The mean and standard deviation of the net incomes for all companies making up a stock index is $3.5 million and $4.2 million, respectively. If a random sample of 49 companies is taken from the index, the standard error of the sample mean is closest to: A. $71,429. B. $85,714. C. $500,000. D. $600,000. | 
发表于 2008-11-5 16:31
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