Question 1142019
SD of the sample = SD of the population divided by the square root of the number of items in the sample:
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SD of the sample = {{{1200/sqrt(30)}}} = {{{219.09}}}
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Take 7500 and subtract the mean of 7200 to get a result of 300.  Divide 300 by the SD of the sample (219.09) to get a result of 1.37.  Look up +1.37 on a z-table to get a result of 0.9147.  This means there is a 0.9147 probability that the mean daily revenue for the next 30 days will be below $7500.
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Take 7000 and subtract the mean of 7200 to get a result of -200.  Divide -200 by the SD of the sample (219.09) to get a result of -0.91.  Look up -0.91 on a z-table to get a result of 0.1814.  This means there is a 0.1814 probability that the mean daily revenue for the next 30 days will be below $7000.
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To find out the probability that the mean daily revenue for the next 30 days will be between $7000 and $7500, simply subtract the probability that the mean daily revenue is less than $7000 (0.1814) from the probability that the mean daily revenue is less than $7500 (0.9147) to get a result of 0.7333.
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So, the answer is (C).