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Using A Statistics Formula To Establish Confidence Intervals of a Poll

When political polls are conducted, a confidence interval is always included. This confidence interval is referred to as a margin of error.   For example, Rassmussun Poll Data showed Arnold Schwarzenegger trailing State Treasurer Phil Angelides by one percentage point, 45% to 44% in the California governors race, where the sampling error for the survey was +/- 4.5 percentage points at the midpoint with a 95% level of confidence. Given the 4.5% error, the 1% edge is insignificant. A respected pollster like Rassmussun will use proper survey methods to insure a good sample. The mathematics and statistics used to establish the confidence interval is fairly straightforward, but involves a somewhat large formula.

The Confidence Interval Formula

In this formula, each variable stands for a quantity obtained from the survey or a calculated quantity.  For example, n would be the sample size, and zc would be a z-scored calculated using another formula. You are basically substituting into several different formulas to obtain the results. A student with little or no algebra background would find this formula a bit intimidating.  A student completing several years of algebra would not have difficulty working this formula however. An example where this formula is used is given here.

I think you can see why the average first year introductory statistics course in college requires 1 or 2 years of algebra.  And, statistics is required for most degrees, even non-science and non-math degrees.


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