Statistics for Environmental Engineers

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15


25


30


14


11


19


17


31


2


3,500,000


0.35


10


40


36


41


29


48


33


37


30


44


45


3


2,500,000


0.25


8


60


58


34


51


39


53


57


69

Find the total amount of phosphorus in the reservoir, its average concentration, and its standard error.


23.8 Precision Guidelines. Some years ago the National Council for Air and Stream Improvement (NCASI) proposed the following guidelines for monitoring pulp and paper mill waste streams.


Monitoring Objective


Maximum Error (%)


Exploratory survey to locate areas of heavy pollution


± 40


Evaluate unit process efficiency


± 5


Estimate design loads for wastewater treatment


±10


Evaluate pollution prevention projects


± 5-10


Monitoring for effluent compliance


±5


Monitoring for stream standards


±5-10


Monitoring to assess sewer charges


±5

Use the following 12 observations to estimate the standard deviation and determine the required sample size for (a) exploratory survey, (b) design load estimation, and (c) sewer charge assessment.


3160, 2140, 1210, 1400, 2990, 1420, 2000, 2610, 2720, 2700, 2900, 3390


23.9 Coliforms. Use the data from Exercise 19.4 to determine the sample size necessary to estimate the proportion of wells that contain coliform bacteria (MF method) with a 95% confidence interval no larger than ±0.05. Use a planning value of p = 0.15. Would you use the same sample size to estimate the proportion of wells that contain coliforms as indicated by the Colilert method?

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