We tested the hypothesis that the transect % TDG values (total dissolved gas as percent

saturation) were greater than the fixed monitor % TDG values using Equation 7. We

hypothesized that *H*0:D ≤ 0 with alternative *H*1:D > 0. We rejected *H*0 if *t*0 > tα,*n*1. Again,

using α = 0.05 and υ = *n * 1 = 7 (determined by the sample size of 8), the value of tα,*n*1

= *t*0.05,7 = 1.895.

Also, since 5.9 = *t*0 > *t*α,*n*1 = *t*0.05,7 = 1.895, we rejected *H*0 and concluded that the difference

between the transect values and the fixed monitor station values was greater than zero. The fixed

monitor consistently recorded total dissolved gas percent saturation values that were less than the

average of those actually present in the river at this location during this study. Thus, we

conclude that the fixed monitor system does not accurately represent the flux of total dissolved

gas in the river.

To avoid tedious hand calculations, software packages are useful for calculating the paired

t-test statistics for the data sets. Two commonly used packages are SPSS (SPSS Inc., Chicago

IL) and SAS (SAS Institute, Inc., Cary, NC).

The technique employed in the above example can be used to look at an entire monitoring

system. Though the fixed monitoring system is designed to determine extreme concentrations of

total dissolved gas in spill waters, here we explore the potential of each station for use in

monitoring the average total dissolved gas concentration in the river. The system consists of

monitors at 26 sites. As in example 1, these fixed monitor sites were compared with transect

data collected during 1995.

Again, because the transect study was designed to aid modelers and not strictly to verify the

fixed monitor system, adequate data were not available for each location. The analysis shown

here was intended only to provide insight into the representativeness of the monitoring system.

Details, such as verifying normality, have been omitted. The results presented here might best be

used to design future, more rigorous verification studies.

Transects within 3.5 km of each fixed monitor site were used for comparisons to fixed

monitor data. This created a larger data set than if only transects that were adjacent to

the monitor sites were used. Larger data sets reduce the type II error, that is, the

of data for each site. This constraint eliminated three stations, leaving 23 for further

possible analysis.

Because of the number of comparisons that were desired, SPSS was used to analyze the data.

A paired t-test was run on each of the 23 fixed monitor sites and their comparable transect data.

The results of these analyses are shown in Table 3.

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