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A sample produces x-bar = 7 with an error bound of EBM = 2.5. What is the resulting confidence interval?
A(2.5, 7.0)
B(7.0, 9.5)
C(4.5, 9.5)
D(4.5, 7.0)
Answer & Solution
Correct answer: C. (4.5, 9.5)
1. A confidence interval takes the form (x-bar - EBM, x-bar + EBM).
2. Lower bound: 7 - 2.5 = 4.5.
3. Upper bound: 7 + 2.5 = 9.5.
4. Options B and D only apply the error bound to one side of x-bar instead of both, so they are incomplete.
_Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 8 "Confidence Intervals", section 8.1 A Single Population Mean using the Normal Distribution_
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