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This applet generates confidence intervals for means or proportions. The options for confidence intervals for means include “z with sigma,” “z with s,” or “t.” The options for confidence intervals for proportions are “Wald,” “Adjusted Wald,” or “Score.” Users set the population parameters, sample size, number of intervals, and confidence level. Click "Sample," and the applet will graph the intervals. Intervals shown in green contain the true population mean or proportion, while intervals in red do not. The true mean or proportion is shown by a blue line. The applet displays the proportion of intervals containing the population parameter for each sample and a running total of all the samples. Users can also click on a particular interval to display the numerical interval or sort the displayed confidence intervals from smallest to largest. This applet is part of a collection designed to accompany the textbook “Investigating Statistical Concepts, Applications, and Methods” (ISCAM) and is used in Exploration 4.3 on page 327, Investigation 4.3.6 on page 331, and Exploration 4.4 on page 350. This applet also supplements “Workshop Statistics: Discovery with Data,” 2nd edition, Activity 19-5 on page 403. Additional materials written for use with these applets can be found at and
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Date Of Record Creation 2007-02-20 12:40:58
Date Of Record Release 2005-06-20 13:27:33
Date Last Modified 2007-07-24 18:53:24
Statistical Topic
Material Type
Author Name Allan Rossman, Beth Chance
Author Organization California Polytechnic State University
Technical Requirements Java Applet
Comments This applet provides a useful visual representation of calculating confidence intervals for means and proportions and can help enhance students’ understanding of confidence and confidence intervals. Teachers without the associated textbooks will have to spend some time preparing materials and activities to accompany the applet so that students get the most benefit.
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