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Statistics Confidence Intervals Question?

  1. Dec 5, 2013 #1
    1. The problem statement, all variables and given/known data
    A Gallup Poll of 1002 adults in October 2002 found that 25% of the respondents said that their household
    had experienced a crime in the past year. Among respondents aged 18-29 years, 43% had been victims of a
    crime. Gallup says, “For results based on the total sample of national adults, one can say with 95%
    confidence that the margin of sampling error is +/- 3 percentage points.” Is the margin of error for adults
    aged 18-29 smaller than, larger than, or the same as +/- 3 percentage points?

    2. Relevant equations

    3. The attempt at a solution
    Well, I think because of the smaller sample size, the margin of error would be larger because it is less precise. Yet, this sample size comes from a larger sample size with a given confidence interval width, so I am not sure.
  2. jcsd
  3. Dec 6, 2013 #2


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    Science Advisor

    Hi mintsapple!

    Do you know how to calculate the confidence limit that Gallup provided? Can you calculate how big a sample of 18-24 year olds yu would need to get the same confidence interval?
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