This preview shows pages 1–2. Sign up to view the full content.
Power analysis using “Java applets for power and
sample size”
ESM 206
Nov. 19 2007
The most useful of the online power analysis tools is at
http://www.math.uiowa.edu/~rlenth/Power/
.
We will learn how to use this using the one
sample ttest from the first question on the problem set (calcium concentrations).
Navigate to the site.
Prominently displayed near the upper left of the page (below the
cow) is a section titled “Select the analysis to be used in your study.”
Java takes a
moment to load, and then you will see a list of tests for which you can do a power
analysis.
Select “Onesample t test” and click “Run selection.”
You will see the
following:
Resize it so that you can see everything on the bottom.
On this screen, sigma is the standard deviation of the data, “True mu  mu_0” is the
effect size, n is the sample size, power is 1
β
, and alpha is
α
.
You can adjust the first 4
with the sliders, and the last with the dropdown box.
For these data, sigma is 1.787.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 KENDALL,BERKLEY
 Environmental Science

Click to edit the document details