Question 5 • EHS Content Recovery - Probability and Statistics - Part D
A statistics class weighed 20 bags of grapes purchased from the store. The bags are advertised to contain 16 ounces, on average. The class calculated the 90% confidence interval for the true mean weight of bags of grapes from this store to be (15.875, 16.595) ounces. What is the sample mean weight of grapes, and what is the margin of error?
Answer
A
The sample mean weight is 15.875 ounces, and the margin of error is 16.595 ounces.
B
The sample mean weight is 16.235 ounces, and the margin of error is 0.360 ounces.
C
The sample mean weight is 16.235 ounces, and the margin of error is 0.720 ounces.
D
The sample mean weight is 16 ounces, and the margin of error is 0.720 ounces.
Explanation
The sample mean is the midpoint of the confidence interval: (15.875 + 16.595) ÷ 2 = 16.235 ounces. The margin of error is the distance from the midpoint to either endpoint: 16.595 − 16.235 = 0.360 ounces. Therefore, choice B gives both values correctly.
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