Problem-Solving and Data AnalysisHardWhat barely affects a margin of error
Problem-Solving and Data Analysis practice question
Which of the following has the LEAST effect on the margin of error of a well-conducted random sample survey?
- A. The size of the population, once the population is much larger than the sample.Correct
- B. The size of the sample.
- C. The confidence level chosen for the interval.
- D. How much the population varies on the quantity being measured.
Answer: A. The size of the population, once the population is much larger than the sample.
A random sample of 1,000 works about equally well for a city of a million or a country of fifty million. What matters is the sample size, the confidence level and the population's variability.
Why the other answers are wrong
- B. The size of the sample.
- Sample size is the main lever: larger samples give smaller margins.
- C. The confidence level chosen for the interval.
- A higher confidence level widens the interval.
- D. How much the population varies on the quantity being measured.
- More variable populations need larger samples for the same margin.
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