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Survey Sample Size and Confidence Intervals

Activity Description Activity Guide


This two-part activity addresses margins of error of surveys, and explores relationships between confidence intervals and both sample sizes and proportions.

Mathematics Topics: This activity involves one-proportion z-tests, 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
N=100
+ 10
N=200
+ 7
N=500
+ 4.3
N=1000
+ 3
N=10000
+ 1

Figure 2. The relationship between sample size and confidence interval


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Last modified on August 15, 2001.