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**Java Applets for Power and Sample Size

This collection of free, interactive Java applets provides a graphical interface for studying the power of the most commonly encountered experimental designs. Intended to be useful in planning statistical studies, these applets cover confidence intervals for means or proportions, one and two sample hypothesis tests for means or proportions, linear regression, balanced ANOVA designs, and tests of multiple correlation, Chi-square, and Poisson. Each applet opens in its own window with sliders, which are convertible to number-entry fields, for manipulating associated parameters. Controlling for the other parameters, users can change sample size, standard deviation, type I error (alpha) and effect size one at a time to see how each affects power. Conversely, users can manipulate the power for the test to determine the necessary sample size or margin of error. Additional features include a graph option by which the program plots a dependent variable (i.e. power) over a range of parameter values; the graph is automatically updated as the parameters are changed. Each dialog window also offers a Help menu which provides instructions for using the applet. The applets can be used over the Internet or downloaded onto the userís own computer.
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Date Issued 2001
Resource Type
Email Address
Date Of Record Creation 2005-02-12 22:49:53
Date Of Record Release 2005-02-12 22:49:53
Date Last Modified 2007-07-24 18:38:26
Statistical Topic
Material Type
Author Name Russ Lenth
Author Organization University of Iowa
Technical Requirements Java Runtime Environment (JRE)/Java Development Kit (JDK) to run locally; Java 1.1 for Internet use.
Comments This material is a great resource for doing power and sample size calculations. The combination of visual tools, such as dynamically updating sliders and fully customizable graphing capability, make this item a strong visual aid for teaching power. Unfortunately, because the applets are not intended for instructional use, teachers will have to create materials to accompany these applets for classroom and homework situations.
Source Code Available 1
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