Geoscience Reference
In-Depth Information
h e result
h=0
means that we cannot reject the null hypothesis at a 5%
signii cance level. h e
p
-value of 0.1071 or ~11% (which is larger than the
signii cance level) means that the chances of observing either the same
result or a more extreme result, from similar experiments in which the null
hypothesis is true, would be 11 in 100.
We can use the same script to test whether the two samples in
organicmatter_
two.mat
come from the same lithological unit (
null hypothesis
) or from
two dif erent units (
alternative hypothesis
) without requiring a normality
assumption for the underlying population. We clear the workspace and load
the data.
clear
load('organicmatter_two.mat');
Alternatively, we can use the function
ranksum
to perform a Mann-Whitney
test on the same samples:
[P,H,STATS] = ranksum(corg1,corg2)
which yields
P =
0.5906
H =
0
STATS =
zval: 0.5380
ranksum: 3733
h e result
h=0
means that we cannot reject the null hypothesis at a 5%
signii cance level without another cause. h e
p
-value of 0.5906 or ~59%
(which is much larger than the signii cance level) means that the chances
of observing either the same result or a more extreme result from similar
experiments in which the null hypothesis is true would be 5,906 in 10,000.
3.12 The Ansari-Bradley Test
h e Ansari-Bradley test introduced by Abdur R. Ansari and Ralph A.
Bradley (1960) can be used to determine whether two samples come from
the same distribution (
null hypothesis
), or whether the samples come from
distributions with the same median and shape but dif erent dispersions
(e.g., variances) (
alternative hypothesis
). In contrast to the
F
-test, which
