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Homework Help: Statistics Confidence Intervals

  1. Mar 13, 2009 #1
    1. Polotical parties rely heavily upon polling to measure their supports in the electorate. Below are the results of a poll conducted in 1996 for four (i only listed the one needed) political parties.
    Level Count Probability Stderr Prob
    N 250 .211 .0119
    Total 1193
    4 levels

    2. Construct and interpret a 95% confidence interval for the level of support for the N Party in 1996

    I only know how to do confidence intervals when a mean ans standard deviation is given using the formula : Mean+- Z*(Sq rt(sx/n)
    Last edited: Mar 13, 2009
  2. jcsd
  3. Mar 14, 2009 #2


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    Homework Helper

    The outline for a confidence interval for a proportion is

    Point estimate +/- margin of error

    You're given the point estimate, the sample size, and standard error. Look in your book to find how to find the margin of error from this information.
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