Stockpile Statistics Worksheet

Stockpile Statistics Worksheet

328 Sampling and Analysis of Environmental Chemical Pollutants Appendix 14 Stockpile Statistics Worksheet Stockpile Statistics Worksheet Step 1 Nu...

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Sampling and Analysis of Environmental Chemical Pollutants

Appendix 14 Stockpile Statistics Worksheet

Stockpile Statistics Worksheet Step 1

Number of collected samples



n n P

Step 2

Calculate sample concentration mean x n ¼ number of samples

xi x ¼ i¼1 n

x¼ 

n P

s2 ¼ i¼1 pffiffiffiffi s ¼ s2

x 2i 

n P

2 xi

i¼1

n

s2 ¼

Step 3

Calculate sample variance

Step 4

Calculate sample standard deviation

Step 5

Calculate degree of freedom

Step 6

Calculate standard error of the mean

Step 7

Obtain Student’s t value corresponding to the degree of freedom value determined in Step 5

Look up Table 1, Appendix 1, for the selected t-value

ta ¼

Step 8

Calculate the confidence interval

CI ¼ x+ta sx

CI ¼

Step 9

Obtain action level (regulatory threshold) Ca for the contaminant of concern

Ca

Ca ¼

Step 10

Calculate the difference

D ¼ Ca  x

Step 11 Step 12

Determine minimum sufficient number of samples

df ¼ n  1 sx ¼ psffiffi n

nmin ¼

Decide whether the number of samples is sufficient

n1

t2a s2 2

s¼ df ¼ sx ¼

D¼ nmin ¼

D

nmin 5n

Yes

nmin 5n

No

The contaminant of concern is not present in the stockpile above the action level if the upper limit of the CI is less than the Ca .

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