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Data Analysis and Statistics for Geography, Environmental Science, and Engineering
book

Data Analysis and Statistics for Geography, Environmental Science, and Engineering

by Miguel F. Acevedo
December 2012
Beginner content levelBeginner
557 pages
19h 5m
English
CRC Press
Content preview from Data Analysis and Statistics for Geography, Environmental Science, and Engineering
125Exploratory Analysis and Introduction to Inferential Statistics
If we relax the effect size to the difference 45.7 − 44, i.e., a delta 2, the power goes up to 0.79.
We conclude that for this sample the t-test would have relatively low power given α = 0.01.
We can now determine how many more observations would be required to raise the power to 0.9
assuming the same variability, same α, and same effect size of delta = 2.
>power.t.test(power=0.9, delta = 2, sd=sd(poro$V1), type=”one.sample”,
alternative = “one.sided”, sig.level=0.01)
We obtain
One-sample t test power calculation
n = 12.30839
delta = 2
sd = 1.702939
sig.level = 0.01
power = 0.9 ...
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Publisher Resources

ISBN: 9781439885017