SOLUTION: A Statistician employed by a consumer testing organization reports that at 95% confidence he has determined that the true average content of the Uncola soft drinks is between 11.7

Question 309469: A Statistician employed by a consumer testing organization reports that at 95% confidence he has determined that the true average content of the Uncola soft drinks is between 11.7 and 12.3 ounces. He further reports that his sample revealed an average content of 12 ounces, but he forgot to report the size of the sample he had selected. Assuming the standard deviation of the population is 1.28, determine the size of the sample.
Answer by stanbon(57984) (Show Source):
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A Statistician employed by a consumer testing organization reports that at 95% confidence he has determined that the true average content of the Uncola soft drinks is between 11.7 and 12.3 ounces. He further reports that his sample revealed an average content of 12 ounces, but he forgot to report the size of the sample he had selected. Assuming the standard deviation of the population is 1.28, determine the size of the sample.
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2E is the width of the confidence interval.
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2E = 12.3-11.7 = 0.6
E = 0.3
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n = [1.96*1.28/0.3]^2
n = 69.93
Rounding up you get n = 70
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Cheers,
Stan H.