Figure 6 is a normal probability plot of the

differences between the transect and fixed

monitor data pairs. Though the data show

some tendency to be lower than the normal

plot for low probabilities and higher than the

normal plot for high probabilities, the data

appear to be approximately normally

distributed.

Equations 2 and 3 were used to test

whether the data collected at the fixed

monitor site represent the water quality

within the river. First, the parameters

necessary for the test statistic were calculated.

The mean difference (Equation 5) was

∑D

20.1

=

= 2.5

(10)

8

The variance was estimated using Equation 6:

I

1F

2

- G∑ D J

af

∑D

K

1

2

60.1 -

2

20.1

8

=

= 1.4

2

8 -1

(11)

The test statistic, *t*0, was then calculated using Equation 4:

2.5

=

= 5.9

1.2

8

(12)

Next, the test statistic calculated in Equation 12 was compared with tα

. This value can be

2,*n*-1

found in various statistics books in the Students' *t *table or *t *distribution table (Hines and

Montgomery 1980, p 596). For α = 0.05 (our choice) and υ = *n * 1 = 7 (determined by the

sample size of 8), the value of tα ,*n*-1 = *t*0.025,7 = 2.365 (from tables). Then, since

2

5.9 = *t*0 > *t*α

= *t*0.025,7 = 2.365

2,*n*-1

(13)

we rejected *H*0 and concluded that the difference between the transect values and the fixed monitor

station values was not zero. The fixed monitor did not adequately represent the water quality in the

river at this location.

8

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