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.

 

[Architeuthis Dux]

I would first like to clarify that the given data is not sufficient to calculate a confidence interval using the formula mentioned. A confidence interval is used to estimate the true population parameter (such as mean or proportion) based on a sample of data. In this case, the given data only includes the count and probability of support, but does not provide information on the mean or standard deviation.

To construct a confidence interval for the level of support for the N Party in 1996, we would need to know the total number of people in the electorate, the sample size used in the poll, and the specific question(s) asked in the poll. With this information, we can calculate the proportion of support for the N Party and use that to construct a confidence interval.

For example, if the total number of people in the electorate is 1 million and the sample size used in the poll is 250, then the proportion of support for the N Party would be 250/1,000,000 = 0.00025. We can then use this proportion to calculate the standard error of the proportion, which is given by the formula: SE = √(p*(1-p)/n), where p is the proportion and n is the sample size.

Once we have the standard error, we can construct a 95% confidence interval using the formula: CI = p ± z*(SE), where z is the critical value for a 95% confidence interval (1.96 for a large sample size).

Interpreting the confidence interval would mean that we are 95% confident that the true proportion of support for the N Party in the electorate falls within the range of the calculated interval. However, it is important to note that the confidence interval is only an estimate and may not accurately reflect the true level of support in the entire population.

In conclusion, while political parties may rely on polling to measure their support in the electorate, it is important to carefully consider the methodology and data used in these polls in order to accurately interpret the results. In this case, the given data is not sufficient to calculate a confidence interval, and more information would be needed to make any meaningful interpretations.