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Method Nitrite Measurements
ISE 0.32 0.36 0.24 0.11 0.11 0.44 2.79 2.99 3.47
Colorimetric 0.36 0.37 0.21 0.09 0.11 0.42 2.77 2.91 3.52

17.3 BOD Tests. The data below are paired comparisons of BOD tests done in standard 300-mL
bottles and experimental 60-mL bottles. Estimate the difference and the confidence interval
of the difference between the results for the two bottle sizes.

300 mL 7.2 4.5 4.1 4.1 5.6 7.1 7.3 7.7 32 29 22 23 27
60 mL 4.8 4.0 4.7 3.7 6.3 8.0 8.5 4.4 30 28 19 26 28
Source: McCutcheon, S. C., J. Env. Engr. ASCE, 110, 697–701.

17.4 Leachate Tests. Paired leaching tests on a solid waste material were conducted for contact
times of 30 and 75 minutes. Based on the following data, is the same amount of tin leached
from the material at the two leaching times?

Leaching Time Tin Leached
(min) (mg/ kg)
30 51 60 48 52 46 58 56 51
75 57 57 55 56 56 55 56 55

17.5 Stream Monitoring. An industry voluntarily monitors a stream to determine whether its goal
of raising the level of pollution by 4 mg/L or less is met. The observations below for September
and April were made every fourth working day. Is the industry’s standard being met?

September April
Upstream Downstream Upstream Downstream
7.5 12.5 4.6 15.9
8.2 12.5 8.5 25.9
8.3 12.5 9.8 15.9
8.2 12.2 9.0 13.1
7.6 11.8 5.2 10.2
8.9 11.9 7.3 11.0
7.8 11.8 5.8 9.9
8.3 12.6 10.4 18.1
8.5 12.7 12.1 18.3
8.1 12.3 8.6 14.1

© 2002 By CRC Press LLC