- Usually used in the laboratory to determine if the CV is within a certain standard deviation (SD)
- Pipette precision - taking several pipette readings and determining the variation within the values taken
- Intra-assay precision - is applied when control samples are placed at regular intervals within a long assay
- Inter-assay precision - the same control sample is run each time an assay is completed
- CV can also be used to determine the % error if you know the mean and it's SD
What is an assay? When assaying laboratory samples (ex. Determination of TSH) controls, with known values, are placed long with the unknown patient data. if the control falls to meet an expected range, then the patient samples will be considered as having inaccurate values. Controls should all be within a certain percentage. An intra-assay value of < 5% is expected. For inter-assay this value should < 10%
- Calculating CV with 1, 2 or 3 SDs (68%, 95%, or 99%)
- The greater the SD value the less precise the data because it increases the acceptable range within the deviation