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Sample Size and Confidence Intervals


 
This twopart activity addresses margins of error of surveys, and explores relationships between confidence intervals and both sample sizes and proportions. Mathematics Topics: This activity involves oneproportion ztests, the associated standard errors of measurement, and confidence intervals. Mathematical Thinking: Students interpret "margin of error," and connect, algebraically and graphically, confidence intervals with sample sizes and proportions. Technology: Students use statistical test features graphing calculators to calculate confidence intervals, and graph and trace functions related to standard errors of measurement. Sample Screenshots: Below are calculator screen shots showing: (1) the input and output of a confidence interval calculation, and (2) a table and a graph showing the relationship between sample size and confidence interval. Figure 1. 95% Confidence Interval Calculation for n=813
Figure 2. The relationship between sample size and confidence interval 

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