Hach AutoCAT 9000, Instruction Manual

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Collecting and Accessing Data
Collecting and Accessing Data
50081_AutomatedTitration.fm
Page 47
5.2.4.1 Calculation of Mean
The mean is calculated using the following equation:
Where:
R
i
is the result from the i
th
replicate measurement (i.e., Test)
N is the number of replicate measurements.
5.2.4.2 Calculation of Standard Deviation (<5 replicate analyses)
When the number of replicate measurements is between 2 and 5, the standard deviation
of the mean, S
Mean
is estimated using the following formula:
Where:
R
max
is the maximum value obtained from the replicate measurements
R
min
is the minimum value obtained from the replicate measurements
Q
is taken from the following table:
5.2.4.3 Calculation of Standard Deviation (>5 replicate analyses)
If more than five replicate measurements (i.e., Tests) are made, the standard deviation of
the mean,
S
Mean
is calculated using the following formula:
The final average is reported as: Mean (± S
Mean
)
Mean
R
i
i 1
=
N
∑
N
-----------------
=
N Q
2 1.128
3 1.693
4 2.059
5 2.326
S
Mean
R
max
R
min
–
Q
---------------------------------
⎝ ⎠
⎛ ⎞
2
N
------------------------------------------
=
S
Mean
R
i
2
i 1
=
N
∑
R
i
2
i 1
=
N
∑
N
-------------------
–
N 1
–
( )
N
--------------------------------------------
=