InfluentialPoints.com
Biology, images, analysis, design...
Use/Abuse Principles How To Related
"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

 

 

Coefficient of variation

 

Coefficient of variation

Worked example

Let us use these weights of zebu cattle as an example.
Cow NumberWeight (kg)
1280
2295
3245
4310
5285
Σ x 1415

Mean Weight () =   283 kg    Standard deviation (s) =   24.14 kg

So :
CV  =   24.14 / 283  =  0.0853
CV (%)  =  100 0.0853  =  8.53 %
CVcor  =  8.53 {1 + (1 / 4 5)}   =  8.70 %

 

Intra- and inter-assay coefficients of variations

Worked example

Cow
No.
PCVsi2MeanCVCV2
1.2.
133352340.042.002
226234.524.50.087.007
329290290.000
432354.533.5.063.004
531284.529.5.072.005
631310310.000
731344.532.5.065.004
83129230.047.002
93533234.042.002
1021244.522.5.094.009
Mean   2.8530.05 .00355

Let's return to the example of two repeated measurements of packed cell volume that we used to demonstrate calculation of the within-subject standard deviation.

By using the root mean square approach:
Within-subject coefficient of variation = (√0.00355) 100 = 5.96%

By dividing the within assay standard deviation
by the overall mean:
Within-subject coefficient of variation = ((√2.85) / 30.05) 100 = 5.62%

The between-subject coefficient of variation is obtained from the variance of the means of the duplicate observations.
Hence between-subject coefficient of variation = √(2 15.47) / 30.05 = 18.5%