Unformatted text preview: scores to be normally distributed with a variance of 225. If 20 applicants are to take the test, ﬁnd an interval in which the sample variance of test scores should lie with probability 0.90. 3. Waiting times at a service counter in a pharmacy are exponentially distributed with a mean of 10 minutes. If 100 customers come to the service counter in a day, approximate the probability that at least half of them must wait for more than 10 minutes. 4. Onehour carbon monoxide concentrations in air samples from a large city average 12 ppm. The standard deviation of carbon monoxide concentrations measured from the last ﬁve air samples was 9ppm. Find the probability that the average concentration in next ﬁve samples selected randomly will exceed 14 ppm....
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 Fall '08
 Kyung
 Statistics, Normal Distribution, Standard Deviation, Variance, carbon monoxide concentrations, server averages

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