ARCADIS Avantic SPR2-330.662.01 Page 2 of 6 Siemens AG
Rev. 02 05.06 CS PS SP Medical Solutions
5 - 2 Function tests
2.2 Calculations 5
Variation coefficient C
For n individual measurements, the coefficient of variation C amounts to:
s = calculated standard deviation
= mean value of all individual measurements
x
i
= measured value of the ith measurements.
1. To obtain the average x, the 4 dose values are added and the sum is divided by 4.
2. To obtain the difference, the average value is subtracted from each individual
measured value and entered into the column provided
Square the differences
3. Add the 4results:
Σ ....................:
4. Divide the sum by 4: ...............
5. Obtain the square root of the new result: Square root S: ..................
6. Divide the square root S by the average value x determined in step 1:
C = =
n
1/2
Σ
i = 1
Measurement Radiation Exposure (x
i
) Average ( ) = Difference*
1
2
3
4
* Disregard the sign if negative numbers are obtained.
Measurement Square of the difference (x
i
- )
2
1
2
3
4
Coefficient of variation C =
S
C = . . . . . . . . . . . . . . . (must be
≤ 0.05)
s
x
x
(x
i
- x)
2
n -1
x
x
x
x
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