Graphics Programs Reference
In-Depth Information
Although MATLAB does not provide a ready-to-use F-test, this hypoth-
esis test can easily be implemented. We fi rst apply this test to two distribu-
tions with very similar standard deviations of 1.3 and 1.2, respectively.
load('organicmatter_four.mat');
The quantity F is defi ned as the quotient between the larger and the smaller
variance. First we compute the standard deviations, where
s1 = std(corg1)
s2 = std(corg2)
yields
s1 =
1.2550
s2 =
1.2097
The F-distribution has two parameters, df1 and df2 , which are the num-
bers of observations of both distributions reduced by one, where
df1 = length(corg1) - 1
df2 = length(corg2) - 1
yields
df1 =
59
df2 =
59
Next we sort the standard deviations by their absolute value,
if s1 > s2
slarger = s1
ssmaller = s2
else
slarger = s2
ssmaller = s1
end
and get
slarger =
1.2550
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