Purpose: The purpose of this program is to illustrate how the
power changes as the mean for the alternative hypothesis changes. This is
done by graphing the distributions for the null and the alternative
hypotheses. A vertical line marks the upper tail of the null distribution
at .05. Power is illustrated by the area of the alternative distribution
to the right of the vertical line.Download: You can download this program from within Stata by
typing search pwrdemo (see
How can I used the search command to search for programs and get additional
help? for more information about using search).
Use of program: To use this program, type pwrdemo # in the Stata command window,
where the number indicates the mean of the alternative distribution.
Suggested values for the mean of the alternative distribution range from -1 to
+5. Both the null and the alternative distributions have a standard
deviation equal to one, and the null distribution has a mean of zero. The
mean of the alternative distribution is supplied by the user.Examples: The following example uses a mean of the
alternative hypothesis equal to 1.5. The vertical line indicates the upper
tail of the null distribution when alpha equals .05. Power is illustrated
by the area of the alternative distribution (graphed in red) to the right of the
line.
The following example uses a mean of the alternative hypothesis equal to -1.
