SOLUTION: A travel agency call Centre wants to know the average of calls received by its call Centre. A random sample of 21 days is selected and the sample mean number of calls received was
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Question 1145329: A travel agency call Centre wants to know the average of calls received by its call Centre. A random sample of 21 days is selected and the sample mean number of calls received was found to be 166.2 with a sample standard deviation of 22.8 calls. Assume that calls received daily are normally distributed.
Find the 99% confidence interval for the mean number of daily calls received by the call Centre. Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! alpha(a) = 1 - (99/100) = 0.01
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critical probability(p*) = 1 - (a/2) = 0.995
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since the sample(21 days) < 30 and the population standard deviation is unknown, we find the critical value(CV) using the t statistic
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degrees of freedom(DF) = 21 - 1 = 20
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Using p* and DF, the CV is 2.845
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standard error(SE) = sample standard deviation/square root(sample size) = 22.8/square root(21) = 4.975
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Margin of Error(ME) = CV * SE = 2.845 * 4.975 = 14.15 is approximately 14.2
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The 99% confidence interval for the mean number of daily calls received by the call Centre is 162.2 + or - 14.2 or (176.4, 148)
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