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ANOVA (ANOVA)
Computes a one-way analysis of variance for comparing the means of 2 to 20
populations. The ANOVA procedure for comparing these means involves
analysis of the variation in the sample data. The null hypothesis
H
0
:m
1
=m
2
=...=m
k
is tested against the alternative H
a
: not all m
1
...m
k
are equal.
The ANOVA test is a method of determining if there is a significant difference
between the groups as compared to the difference occurring within each
group.
This test is useful in determining if the variation of data from sample-to-sample
shows a statistically significant influence of some factor other than the variation
within the data sets themselves. For example, a box buyer for a shipping firm
wants to evaluate three different box manufacturers. He obtains sample boxes
from all three suppliers. ANOVA can help him determine if the differences
between each sample group are significant as compared to the differences
within each sample group.
ANOVA 2-Way (ANOVA2way)
Computes a two-way analysis of variance for comparing the means of two to 20
populations. A summary of results is stored in the stat.results variable.
The two-way ANOVA analysis of variance examines the effects of two
independent variables and helps to determine if these interact with respect to
the dependent variable. (In other words, if the two independent variables do
interact, their combined effect can be greater than or less than the impact of
either independent variable additively.)
This test is useful in evaluating differences similar to the ANOVA analysis but
with the addition of another potential influence. To continue with the ANOVA
box example, the two-way ANOVA might examine the influence of box material
on the differences seen.
Selecting an Alternative Hypothesis (
ƒ
< >)
Most of the inferential stat editors for the hypothesis tests prompt you to select
one of three alternative hypotheses.
The first is a ƒ alternative hypothesis, such as m0 for the zTest.
The second is a < alternative hypothesis, such as m1<m2 for the
2-SampletTest.
The third is a > alternative hypothesis, such as p1>p2 for the 2-PropzTest.
Lists&Spreadsheet Application 351