GROUP 4
WRITTEN REPORT
One way ANOVA (Analysis of Variance)
(F-Test)
Analysis of Variance:
•
A test of hypothesis that is appropriate to compare means of a continuous
variable in two or more independent comparison groups.
•
A test that provides a global assessment of a statistical difference in more than
two independent means
When will we use this type of test?
•
For example, in some clinical trials there are more than two comparison groups.
In a clinical trial to evaluate a new medication for asthma, investigators might
compare an experimental medication to a placebo and to a standard treatment
(i.e., a medication currently being used).
Anova technique applies:
•
When there are two or more than two independent groups.
Since there are more than two groups, however, the computation of the test statistic is
more involved. The test statistic must take into account the sample sizes, sample
means and sample standard deviations in each of the comparison groups.
The fundamental strategy of ANOVA is to systematically examine variability within
groups being compared and also examine variability among the groups being
compared.
The null hypothesis in ANOVA is always that
there is no difference in means
.
The
research or alternative hypothesis is always that
the means are not equal
and is
usually written in words rather than in mathematical symbols.
•
H
0
: μ
1
= μ
2
= μ
3
= μ
4
•
H
1
: The means are not all equal.
Test STATISTIC for Anova:
The test statistic for testing H
0
: μ
1
= μ
2
= ... =
μ
k
is:
DECISION RULE
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