

Developers: Dr. John Behrens
and Dr. Chong Ho Yu
Software: XlispStat
Media: Interactive simulations
 Description: Statistical
power, which involves the relationship among alpha, beta, effect size,
and sample size, are very difficult to understand. This simulation
written in XlispStat enables students to visually explore the
interrelationships among those variables in a "whatif" manner. To be
specific, in the simulation users can manipulate effect size, sample
size, and alpha level from the lower panels, and the corresponding
changes of power and beta will appear on the upper window. The value of
power is printed on the upper left box whenever an input is made. Alternatively, you
can view an animated demo of the program.
You may also move the mouse over different parts of the following graph to learn about the basic components of statistical power analysis.
Instructions for downloading and running the program:
 Download the compressed program. The archive should be decompressed by your web browser.
 Click open Xlispstat 50 PPC in the folder Rcode.
 Type (menu) at the > prompt (The bracket must be included).
 Choose Power Simulation from the popup menu.
 Choose the indicator(s) (e.g. power, beta...etc) on the right panel.
 Manipulate effect size, sample size, and alpha level on the left.
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