Statistics Confidence Intervals

[sjooff111]

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
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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)

 

[statdad]

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.