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Problem-Solving and Data AnalysisEasy–MediumInterval from an estimate and margin

Problem-Solving and Data Analysis practice question

A random sample of a hotel's guests gives an estimated mean stay of 6.2 nights with a margin of error of 0.4 nights. Which of the following is the interval of plausible values for the mean stay of ALL the hotel's guests?

  1. A. 5.8 to 6.6 nightsCorrect
  2. B. 6.2 to 6.6 nights
  3. C. 5.8 to 6.2 nights
  4. D. 2.2 to 10.2 nights

Answer: A. 5.8 to 6.6 nights

The interval is the estimate ± the margin: 6.2 − 0.4 = 5.8 up to 6.2 + 0.4 = 6.6.

Why the other answers are wrong

B. 6.2 to 6.6 nights
6.2 to 6.6 uses the margin only above the estimate.
C. 5.8 to 6.2 nights
5.8 to 6.2 uses it only below.
D. 2.2 to 10.2 nights
2.2 to 10.2 uses a margin of 4, ten times too large.

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