The precision of the mean,
expressed as the mean absolute
deviation, is also shown in Table 2. The
Levene’s test reveals that, for methane,
ethane, nitrogen, and the GHV, the
deviation is significantly different. The
concentration measurement for propane
is not found to be significantly different.
It can be said that measurements carried
out on system one are equally or more
precise than those on system two.
When these results are compared
with expectations regarding the
influence of partial vaporisation on the
analysis results, the following
is discovered. On system two,
higher concentrations of
lighter components are found
(nitrogen and methane)
accompanied with a lower
GHV. Also, a higher deviation
compared to system one and
abnormal distributions can be
found in the data. These might
be indications that partial
vaporisation is occurring in
system two.
Other reasons for
differences in the mean can be
found in the assumption that
Figure 7.
Combined gross heating value (GHV) for system one (left) and system two (right).
Table 2.
Means with deviation and Wilcoxon and Levene’s test results for system one and two
System one (n=99)
System two (n = 99)
Means
compared
Variance
compared
Mean of
measurements
Mean absolute
deviation
Mean of
measurements
Mean
absolute
deviation
Wilcoxon
α
= 0.05
Levene’s
α
= 0.05
Methane (mol%) 93.476
0.046
93.500
0.089
Different
Different
Ethane (mol%)
6.315
0.053
6.287
0.093
Different
Different
Propane (mol%) 0.0124
0.0002
0.0115
0.0003 Different
Equal
Nitrogen (mol%) 0.197
0.0108
0.202
0.0161
Different
Different
GHV (MJ/m
3
)
39.520
0.018
39.509
0.029
Different
Different
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