Of the non-reservation
sites, 147 had enough data to permit analysis with the T test. The available data does not show that the
number of changing, increasing and decreasing sites is more than would be
expected by chance. The Sen and
Mann-Kendall tests give similar findings.
The Mann-Kendall test does gives some evidence of homogeneity of trend
across sites in this case; however, there is no evidence that this trend is
anything but randomly fluctuating.
An important reason for lack
of significance in the off-reservation sites appears to be that the latter have
been monitored for a much shorter period of time, so that sample variances are
much larger. This makes it more
difficult for the set of readings at a site to pass a T-Test. Results for CH4 levels at
non-reservation sites are summarized in Tables 6 and 7.
Table 9. Summary of T-Test
results, CH4_LEL for 147 off-reservation sites.
|
Significance Level |
Number of Sites with Upward Trend |
Number of Sites with Downward Trend |
Number of Sites with Any Trend |
Expected Number of Sites with Any Trend |
|
99.9% |
0 |
0 |
0 |
0 |
|
99.0% |
0 |
2 |
2 |
1 |
|
95.0% |
0 |
2 |
2 |
7 |
Table 10. Summary of T-Test
results, log(CH4_LEL) for 147 off-reservation sites.
|
Significance Level |
Number of Sites with Upward Trend |
Number of Sites with Downward Trend |
Number of Sites with Any Trend |
Expected Number of Sites with Any Trend |
|
99.9% |
0 |
0 |
0 |
0 |
|
99.0% |
0 |
0 |
0 |
1 |
|
95.0% |
1 |
0 |
1 |
7 |
Table 11. Sen and Mann-Kendall
statistics, CH4_LEL for 147 sites off 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% |
3 |
0 |
3 |
1 |
|
95.0% |
9 |
1 |
7 |
4 |
Chi-square estimate of homogeneity for the Mann-Kendall scores: about 59%.