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LeMasters, Gary S.; Doyle, Douglas J. / Grade A dairy farm well water quality survey
[DNR-058] (1989)

Methods,   pp. 3-10 PDF (430.5 KB)


Page 8

where
0.05        the specified probability that the interval will not
contain the true value with repeated samples.
A
V(p)1/2     =     Standard Error of the proportion estimator.
For a 95% confidence interval this reduces to (ibid.):
AA
[IN- 1.96 (S.E.)   Ps  __ p, + 1.96 (S.E.)]
Pesticide Concentrations
The mean concentration estimator for pesticides is given by the following
(Scheaffer et al., 1979):
A                   A
Y     =     [1/N] Ni Y
where
N      -
Ni     --
A
Yi
The variance
A(
the number of elements in the population.
the number of elements in the ill stratum.
the mean concentration for the ih stratum.
for this estimator is given by the following (ibid.):
[1/N2] : N 2    [N- n-   [-
LNi         niAJ
where
ni     -
Si2
The strata level
A A
V(7) =
the number of sampled elements in the jih stratum.
the variance estimator for the ith stratum.
variance is given by (ibid.):
(y, -A~
ji)2
nj-I1
8


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