pwrdemo2.hlp.htm

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help for pwrdemo2
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Draw Curves Illustrating Power
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Description

  pwrdemo2 draws curves showing the distribution of the null hypothesis,
        and the alternative hypothesis, showing the rejection region
        and the area representing power.  

        By default, when you run pwrdemo2, a dialogue box is brought
        forward with buttons allowing you to vary the sample 
        size (N), the difference between the mean under 
        the null hypothesis and the mean under the alternative 
        hypothesis (diff) and alpha. 

        There are also buttons that allow you to show movies
        which show the impact of N, diff and alpha.
        You can vary the speed of the movie by altering
        the movie delay drop down.

Basic Syntax

  . pwrdemo2

Advanced Syntax

  pwrdemo2 , n(#) diff(#) alpha(#) nodialog

  The options n(#) diff(#) alpha(#) allow you to set the sample size,
  the mean difference between Ho and Ha, and alpha.  If you don't 
  include any options, the default values are...

  n(25)       - sample size of 25
  diff(.25)   - the mean difference between Ho and Ha is .25
  alpha(0.05) - alpha is set to 0.05 (two tailed)

  If you include the nodialog option, the display of the dialogue
  box is suppressed.

Examples

  . pwrdemo2
  Starts the program and brings up the dialogue box with the default
  values for n, diff and alpha.

  . pwrdemo2 , n(100)
  Uses a sample size of 100, and the default difference of .25 and alpha of 0.0
> 5 .

  . pwrdemo2 , n(100) diff(.15) alpha(0.01)
  Uses a sample size of 100, a difference of .15 between Ho and Ha, and
  alpha of 0.01

More Advanced Syntax

  pwrdemo2 , n(#) diff(#) alpha(#) t1( ) t2(  ) l1( ) <other grap
> h options>.

  You can use the t1 option to specify the t1title in the graph, the t2 opt
> ion
  to specify the t2title in the graph, and l1 option to specify the l1title
  in the graph.  See help graph for more information on these title options. 
  You can include other graph options to control how the graph looks.

More Advanced Syntax Examples

  . pwrdemo2 , n(100) diff(.15) alpha(0.01) t1("My Power Graph") 
  The t1title in the graph will be "My Power Graph"

Author
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     Statistical Consulting Group
     Institute for Digital Research and Education, UCLA
     idrestat@ucla.edu