Of the 133 sites with
sufficient data for the T-tests, there were many more sites showing change
(both upward and downward trends) in measured O2 than could be
explained by chance. The number of
sites showing significant downward trends outnumbered that showing significant
upward trend. This conforms to the
results for methane levels, since decreases in oxygen are expected to accompany
increases in other gases such as methane.
However, the figures in Tables 4–6 do not match exactly those in Tables
1–3. The relationship between decreasing
oxygen and increasing methane could be confirmed by correlating the significance
level of trend at each site.
Table 4. Summary of T-Test
results, O2 for 133 sites on the Southern Ute Reservation.
|
Significance Level |
U
Number
of Sites with Upward Trend |
D
Number
of Sites with Downward Trend |
U+D
Number
of Sites with Any Trend |
Expected
Number of Sites with Any Trend |
Probability
of D out of U+D Sites Decreasing (see
Note 3) |
Probability
of U+D Sites with Any Trend (see
Note 2) |
|
99.9% |
6 |
21 |
27 |
0 |
0.003 |
1.08E-53 |
|
99.0% |
16 |
31 |
47 |
1 |
0.020 |
1.02E-58 |
|
95.0% |
34 |
41 |
75 |
7 |
0.244 |
3.59E-61 |
Table 5. Sen and Mann-Kendall
statistics, O2 for 183 sites on the Southern Ute Reservation.
|
Significance Level |
Sites
with Positive Sen estimator |
Sites
with Negative Sen
estimator |
Sites with Positive Mann-Kendall statistic
|
Sites
with Negative Mann-Kendall statistic |
|
99.0% |
9 |
44 |
10 |
51 |
|
95.0% |
11 |
60 |
17 |
65 |
Chi-square estimate of
homogeneity for the Mann-Kendall scores: less than 0.0001%