Page 213 - Statistics for Environmental Engineers

l1592_frame_Ch23 Page 213 Tuesday, December 18, 2001 2:44 PM

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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