A traffic engineer is trying to measure the effects of carpool-only lanes on the expressway. Based on a sample of 100 cars at rush hour, he finds that the mean number of occupants per car is 2.5, and the sample standard deviation is 0.4. What is the standard error of the sample mean?
The standard error of the sample mean when the standard deviation of the population is not known is estimated by the standard deviation of the sample divided by the square root of the sample size. In this case, 0.4 / √100 = 0.04. | 
发表于 2011-3-4 14:40
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